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In his column today, Doug Glanville takes a look at Mark Teixeira, a player who didn't find a position until he got to the majors. Not finding a true defensive home until reaching the majors is nothing new. When it comes to signing amateur players, tools and athleticism rule the day, and the difficulty of each position needs to be accounted for. The best athlete on a high school team plays shortstop, but once you drop that player into professional baseball, he might only be a first baseman. With that in mind, here are five big-name prospects who will likely end up at a different position than the one they are playing in the minors.

Dustin Ackley, 2B, Mariners: The second overall pick in the 2009 draft might just be the most interesting defensive case in the minors. He was primarily a first baseman during his college career at North Carolina, but that was because he was recovering from Tommy John surgery and couldn't throw. He's a plus-plus runner with up-the-middle athleticism, and while most teams thought center field was his most logical landing spot, the Mariners initial play is second base, a position at which he has no experience. Though he's been struggling with his bat at Double-A this year (he's hitting .153), scouts say he looks surprisingly comfortable with the glove.

Pedro Alvarez, 3B, Pirates: Like Ackley, Alvarez is also a second overall pick (2008) with questions about his ultimate defensive home. Nobody has questions about his bat, but at 6-foot-3, 225 pounds (and probably more than his listed weight), his range at the hot corner is a bit limited, although his hands and arm are solid. The Pirates kept him out of winter ball in the offseason so he could focus solely on conditioning, but they're likely just holding off the inevitable move to first base. Expect a Jim Thome-like transition where at least the first few big league years are spent at third.

Jesus Montero, C, Yankees: Montero is one of the best hitters in the minors, period. But if the 20-year-old can't stick at catcher, it's difficult to figure out where his future lies for the Yankees other than as a massive trade chip. First base is Montero's only other option, and Teixeira is signed through 2016. To his credit, Montero wants to be a catcher, and he's putting the time in to improve, but the 6-foot-4, 225-pounder is slow behind the plate, and he's thrown out just one out of 14 attempted base stealers this year at Triple-A Scranton. Few believe he can stick at catcher, but many think he could help in the big leagues at DH this year. However, Montero currently has a .715 OPS, so it's not as if he is banging down the major league door.

Miguel Sano, SS, Twins: Sano was the biggest prize in last year's International market, and the Twins surprised many by giving him a $3.15 million signing bonus. He's listed as a shortstop, but one will notice that few players signed at 16 years old are ever listed as anything but shortstops or outfielders. At 6-foot-3 and 200 pounds, Sano has almost already grown out of shortstop, and could make his debut later this year at third base, with some thinking that right field could be his final destination. He is yet to play a professional game, so this will play itself out over the next few years.

Josh Vitters, 3B, Cubs: The third overall pick in 2007, Vitters is in some ways a younger version of Alvarez. Scouts are mixed on his defense. Some see a solid-but-unspectacular defender at third base that projects as an acceptable big leaguer, while others think he's destined for a move to first base or the outfield. From years of experience covering prospects I've learned that if there are even whispers of a defensive move for a prospect, they tend to happen, as the bar at the big league level is higher than we often realize. Therefore, don't expect Vitters (or Alvarez for that matter) to stick at third.

Kevin Goldstein is an author of Baseball Prospectus.

For prospect hounds, today is the real Opening Day, as 10 full-season minor leagues begin play. Although fans and fantasy players alike are reviewing the 30 big league rosters, those mining for gold in the minors have 120 to review. With that in mind, here are four surprisingly high and low assignments for some of the top prospects in the game.

TOO AGGRESSIVE

Simon Castro, RHP, Padres, Double-A San Antonio: The top pitching prospect in the San Diego system dominated at Low-A last year, but a two-level jump was unexpected. The good news is that he has the fastball velocity (up to 95 mph) and command to succeed here, but one wonders whether this is designed merely to keep him out of the high-octane environment of the California League.

Aaron Crow, RHP, Royals, Double-A Northwest Arkansas: This one is defendable but certainly open to debate. On one hand, he's 23 years old, and it's time to get his career going. On the other hand, after not signing with the Nationals out of the 2008 draft and signing late last year, the only pitching experience he has in the past 20 months is three indy league starts and a handful of appearances in last year's Arizona Fall League. Expect some bumps in the road.

Dee Gordon, SS, Dodgers, Double-A Chattanooga: Although Gordon earned co-MVP honors in the Low Class A Midwest League last year (.301 batting average/.362 on-base percentage/.394 slugging percentage, 73 steals), the one thing that stood out about his game was how he was athletic enough to put up big numbers despite being considerably raw. That combination could catch up to him against this level of competition.

Brett Lawrie, 2B, Brewers, Double-A Huntsville -- Lawrie got a taste of Southern League pitching last year in preparation for the World Cup, in which he played for Team Canada. In 13 games for Huntsville at the end of last year, the 20-year-old hit .269 with one extra-base hit in 13 games. Because he's Canadian, he has less playing experience than most his age, and with a .274/.348/.454 line at Low-A Wisconsin last year, he was good but hardly out of his league.

TOO CONSERVATIVE

Aaron Hicks, OF, Twins, Low-A Beloit: The Twins top prospect and 2008 first-round pick spent the majority of 2009 with the Snappers, and was arguably the top prospect on the circuit, despite an unimpressive line of .251/.353/.382. Still, rarely do players of this magnitude repeat a level, although the Twins are notoriously conservative in their development.

Ryan Kalish, OF, Red Sox, Double-A Portland: Kalish struggled upon his initial exposure to Eastern League pitching but was among the league's top bats during the second half of last year, slugging .571 after Aug. 1. It's hard to say what he has left to prove here.

Buster Posey, C, Giants, Triple-A Fresno: The signing of Bengie Molina was a curious one, as Posey hit .321/.391/.511 last year at Triple-A, so it's not as if there's work to be done offensively. Yes, his defense is a bit unrefined, but his bat is the kind of thing the Giants need at the big leagues now.

Drew Storen, RHP, Nationals, Double-A Harrisburg: Maybe the Nationals just wanted him to get used to saving wins for uber-righty Stephen Strasburg, but after 12 1/3 scoreless innings for the Senators last year as part of a dominant pro debut, is there any other point to putting him back in the Eastern League?

Kevin Goldstein is an author of Baseball Prospectus.

One of the most common questions I've received this month during various radio/television interviews and bookstore events is this one: "When will we see Stephen Strasburg in the big leagues?" By reassigning the right-hander to minor league camp on Saturday, the Nationals made it clear it won’t be Opening Day. So to make an educated guess regarding Strasburg's major league debut, I decided to go back in time eight years to look at the last version of Strasburg.

Back in 2002, folks were talking about Mark Prior the same way we're talking about Strasburg this year. Prior was the best college pitcher in the history of baseball, and anybody who saw him that spring knew he was major league-ready. Prior began that season as a 21-year-old at Double-A West Tenn. He was five months short of his 22nd birthday. This year, Strasburg will start at Double-A Harrisburg in the Eastern League, three months from the same number. And the similarities don't end there. Both were born in San Diego and made their marks at colleges in Southern California, with Prior at USC and Strasburg at San Diego State. Strasburg is listed at 6-foot-4, 220 pounds. Prior is the same weight but one inch taller.

Still, like the Nationals, the Cubs decided not to just throw Prior to the major league wolves but rather let him dominate for a bit in the minors. And dominate he did. In 34 2/3 innings for West Tenn, Prior allowed just 10 earned runs while fanning 55 and allowing just 26 hits. One very quick and dirty stat I use to evaluate minor league pitchers is K/H. It's an imperfect but easy measurement of how well a pitcher is doing the most important thing when it comes to projection -- missing bats. A 1-to-1 ratio is the minimum for true "goodness," and 2-to-1 is utterly dominant. So Prior was pretty dominant. After six Double-A starts, Prior was promoted to Triple-A Iowa, where he struck out 24 in 16 1/3 innings while allowing just 13 hits. Once again, an excellent K/H ratio.

Prior hit the big leagues after those nine minor league outings and was among the best pitchers in the league from day one. He made his debut on May 22 and finished the season with a 3.32 ERA and 147 strikeouts in 116 2/3 innings. We don't need to get into his subsequent arm woes, but remember that Prior was one of the most talented young pitchers we've ever seen.

Because so much of Strasburg's past 24 months have mirrored Prior's days from nearly a decade ago, let's set May 22 as the over/under on his big league debut. And while Strasburg is in the minors, keep an eye on his K/H ratio. Strasburg's success is predicated on missing bats, and if his K/H is below 1-to-1, he's probably not missing enough of them. Like Prior, there's no reason he can't be dominant from day one, let's just hope his career lasts a bit longer.

Kevin Goldstein is an author of Baseball Prospectus.

With Julio Borbon penciled (or more accurately, penned) in as the centerfielder and leadoff man for the Texas Rangers, we can now get down to the nitty-gritty here. How good can he be? His tools profile as a classic old-school CF/No. 1 hitter, so let's check how well those translate on the field. The role Texas envisions for Borbon contains three primary components, so here's a breakdown:

Running: Tools-wise this isn't a problem, as Borbon has 70 speed on the 20-to-80 scouting scale, or "plus-plus." He also knows how to use that speed on the basepaths, stealing 97 bases over the past two years, including 44 last year between the minors and majors combined with an impressive 80% success rate. Defensively, his wheels allow him to cover plenty of ground.

Playing Defense: While his range isn't an issue, as Richard Durrett writes in today's piece for ESPNDallas.com, his arm is. We're not talking Johnny Damon noodle-like arm strength, but we're not talking much better either. It's a liability, but also a common one for players like Borbon. The good news here is that Texas couldn't find a better tutor than Gary Pettis, who despite his offensive shortcomings as a player, is arguably the best defensive outfielder of his generation.

Getting On Base: This is where things might get a bit problematic. Borbon certainly can hit. His career minor league batting average is .310, and he's hit above .300 at every level. His .317 batting average during his big league debut last year is probably a bit fluky, as players just don't hit better in the majors, but there's no reason not to see him flirting with .300 annually. The question really revolves around plate discipline, as leadoff men are expected to work the count and reach base via the walk as well to boost their on-base percentage. For many, the baseline here is a 10% walk rate -- that is, if a player has 500 at-bats, one wants to see a minimum of 50 walks. Borbon's career minor league rate is just 6.6%, although there has been some progress including an 8.1% mark at Triple-A, followed by a shockingly good 9.6% rate with Texas. If this is real progress, it spells great things for the Rangers' chances in the American League West. Unfortunately, the small sample sizes bring up a fear of flukiness, and this spring he's returned to his free-swinging ways, walking just twice in 37 at-bats (5.4%).

Our PECOTA projection system, which uses historical comparables to forecast the future, sees many players similar to Borbon, with the most similar being former Padre Alan Wiggins, as well as current big leaguer Juan Pierre, who has carved out an 11-year career with a similar skill set. If the walks come around, everything could change, but for now, the system sees Borbon hitting a solid-yet-unspectacular .286/.335/.394 at the top of the Rangers' lineup without a lot of growth potential from there. He's the kind of player a team is happy to have, while they keep an eye out for something better.

Kevin Goldstein is an author of Baseball Prospectus.

People love ripping on the New York Mets these days, and let's face it, in some ways they've earned it with back-to-back September swoons in 2007 and 2008, and a 2009 season that was arguably baseball's biggest nightmare of the decade.

So far this spring, things are no better, and if anything, a little weirder. Now shortstop Jose Reyes, who had a miserable 2009 due to a recurring hamstring problem, has been diagnosed with a thyroid issue that will keep him off the baseball field for somewhere between two weeks and two months. That's a crazy big window thanks to a condition that's hard to predict, but even the Mets are making every indication that Reyes won't be at shortstop on Opening Day. And as the club learned last year, he's tough to replace. But there is a decent short-term answer, and it's not the one you think.

The man who is supposed to fill in for Reyes is Alex Cora, a journeyman who hit .251/.320/.310 last year as Reyes' back-up. With that kind of line, it's only makes sense for the Mets to start considering other options. One name that is getting tossed around inside their offices is Ruben Tejada, the club's top shortstop prospect. Now the first reaction is to laugh this off as the worst idea ever (hey, it is the Mets), as we're talking about a 20 year-old who played at Double-A last year and while solid, didn't exactly light things up with a batting line of .289/.351/.381 for Binghamton. Thing is, giving Tejada the job, at least temporarily, might not be such a bad idea.

When one thinks of a Latin American shortstop (Tejada is Panamanian), the expectation is a raw athlete oozing with tools -- but Tejada is the exact opposite. He has a near-zero chance of ever being a star, but at the same time, he's one of the most fundamentally sound 20-year-olds you'll ever see. He works the count, makes consistent contact (59 strikeouts in 553 plate appearances last year), and while his range at the position is merely average, he makes the plays on the balls he gets to. Strikeouts and out-of-control fielding are the things that usually spell doom for a rookie, but Tejada has both of those bases covered, so as long as Reyes is out, why not see what the young player can do?

This wouldn't be another case of the Mets curbing the development of some high-ceiling prospect by rushing him to the majors; Tejada is pretty much all he's ever going to be right now, and he's certainly not going to be worse than Cora.

Kevin Goldstein is an author of Baseball Prospectus.