A lot of wheeling and dealing expected

Positioning is the key to Saturday's NFL draft. For a draft thin on certain positions such as offensive lineman, tight end, safety and pass-rushing defensive end, teams have to be in the right spot to fill their needs.

What that means is trades, which means most teams milking their 15-minute selections talking trades. Which means unpredictable decision making and surprises.

Start at the top. The Chargers may or may not take quarterback Eli Manning. His position is clear; he doesn't want to be in San Diego. He looks at an offense that lost a number of key contributors from a year ago and there's uncertainty as to how those key spots are going to be filled. Conventional wisdom calls for a trade, but this situation isn't conventional.

His father, Archie, is taking one of the hardest positions since John Elway didn't want to go to the Colts in 1983. Chargers general manager A.J. Smith is in a tough spot. If Manning is the best player for this franchise, he can't let a player dictate what his team should do in the draft. The other problem is value. Smith can't accept less than what the Chargers got in the Michael Vick trade three years ago. They received four items -- first- and third-round picks in 2001, a second-rounder in the next year's draft and wide receiver Tim Dwight. The Giants probably won't offer more than a first- and second-rounder and wide receiver Ike Hilliard and their preference is to use the second from the 2005 draft.

That leaves the Browns as the next best suitor. Giving the Chargers players isn't a problem. Browns coach Butch Davis has a good portion of the roster already on the trade block -- Tim Couch, Dennis Northcutt, Earl Little, etc. The Chargers need a lot of the players. The Browns are willing to unload a lot of players. But moving from the first to the seventh pick is a huge drop. The Chargers may just have to take Manning.

The Browns are calling everyone. They want left tackle Robert Gallery. They have a package ready for the Raiders they might be willing to accept, but that won't happen until the Raiders are on the clock. The Raiders could move down and take wide receiver Roy Williams.

Last year, there were seven first-round trades. This year, there could be more. The Patriots figure to move around with their two first-round picks. The Giants could move down if they don't get Manning. The Lions could move down a few spots. The Jaguars want to move up from No. 9 for a wide receiver. The 49ers want to trade down unless one of the defensive tackles falls to them. The list of possibilities is endless.

Here's a list of some of the things to watch for this weekend:

1. This is one of the thinnest drafts in recent years in terms of offensive linemen having an instant impact. It's not that these are bad offensive linemen. The draft is loaded with 6-foot-7, 300-plus pound prospects, but that's the problem. They are prospects. Very few are ready to play immediately, and teams looking for instant starters may be taking their starters of the future. That's good news for Gallery, who is angling to be the No. 1 pick. That's good news for Arkansas right tackle Shawn Andrews, who should go between the 10th and 20th choices. Miami guard/tackle Vernon Carey is getting extra attention because of the shortage of instant starters along the line. Teams will be trading up and down the first round to adjust to those realities.

2. The lack of speed at the cornerback position is causing a lot of first-round maneuvering. Cornerbacks DeAngelo Hall and Dunta Robinson could go in the top 10 because they ran 4.3 40s at the combine back in February. Speed caused a big separation among the cornerbacks because the next corner, Chris Gamble, may go around 24th because he couldn't crack a 4.5 40. Teams needing cornerbacks will be trying to get the 10th pick from the Houston Texans, who are also looking at a cornerback.

3. Here's the value of weight loss. Southern Cal defensive end Kenechi Udeze weighed 370 in high school and had to lose 40 pounds to get a scholarship. He ended up losing around 100 pounds to get the USC scholarship. He built himself back into a 281-pound sack machine and a top 10 pick. Arkansas' Andrews weighed 402 in late January because he was taking medication to shrink polyps in his nose. He's trimmed down to 345 and is hot, expected to go somewhere in the middle of the first round.

4. The wide receiver class is going to pay a price for being so good. Six to eight receivers could go in the first round, but this class is so good, teams will wait longer to take them. Some will skip a receiver in the first round and take one in the second. Good receivers will be there in the second round. Larry Fitzgerald is set to be the third pick and Roy Williams will be the receiver teams will be trading for in the top seven or eight. Reggie Williams, Lee Evans, Michael Clayton and Michael Jenkins will pay a price and drop because other positions will be chosen. The benefactors will be the Chiefs and Panthers at the bottom of the first round because they can get an Evans or a Jenkins and maybe even a Clayton at the bottom of the first.

5. The Patriots are the hardest team to project because they will be all over the place. They solved their most pressing need by acquiring halfback Corey Dillon for a second-round pick. With the 21st and 32nd picks, the Patriots are moving those choices. They want to preserve that low pick in the round to take an offensive lineman (Chris Snee or Justin Smiley), an inside linebacker, a defensive tackle or a safety. They will try to trade up from the 21st pick but will fall short of getting safety Sean Taylor. They may peddle that pick for a pick this year and a first rounder next year.

6. Halfback Steven Jackson is playing a big part in this draft. The Broncos have a chance to get him at No. 17, but the Lions or Raiders could trade back to take him higher. The Bucs could take him at No. 15. It's not out of the question for the Cowboys to trade up, but they will more likely wait for an offensive lineman at the 22nd pick or take Michigan halfback Chris Perry.

7. Expect surprises. Don't be surprise if Western Michigan's Jason Babin slips into the lower part of the first round. The Packers and Rams could be interested. Don't be surprised if a safety -- Bob Sanders of Iowa or Sean Jones of Georgia -- slips into the low first. There may be a surprise defensive tackle in the lower first -- Tank Johnson of Washington, Darnell Dockett of Florida State, Isaac Sopoaga of Hawaii, Igor Olshansky or Junior Siavii of Oregon.

8. Last year was a draft loaded with defensive tackles but their productivity wasn't that good. So this year's class will suffer. That's why Vince Wilfork of Miami and Tommie Harris of Oklahoma may not go until the middle of the first round. Marcus Tubbs of Texas may slip into the 20s. That may be a steal for teams such as the Bears, the 49ers and the Seahawks. Another bargain could be defensive end Will Smith falling to as low as the Vikings at No. 19 or the Bears at No. 14.

9. More veterans could be included in draft day trades. The list starts with Cowboys guard Larry Allen, Steelers linebacker Jason Gildon, Browns safety Earl Little and wide receiver Dennis Northcutt, Eagles guard John Welbourn and others. More could be included.

10. Decisions by teams will affect the futures of several veteran quarterbacks. Rich Gannon could be gone in Oakland if Eli Manning falls to the Raiders with the second pick. Drew Bledsoe has to wonder about his long-term future in Buffalo if Ben Roethlisberger falls to No. 13. Philip Rivers could jeopardize Tommy Maddox's long-term future in Pittsburgh if he's available at No. 11. And it's not out of the question for the Bucs to surprise everyone by trading up to get Rivers. One player not too worried is Brett Favre of the Packers. He'll probably play several more seasons, and the Packers aren't expected to take J.P. Losman of Tulane with their first round pick.

John Clayton is a senior NFL writer for ESPN.com.