The Astros are the first team to change leagues since the Brewers moved from the AL to the NL in 1998.
Here are a few of the storylines we’ll be focused on throughout tonight’s game.
Matt Harrison Stats to Know
Harrison’s emergence into an elite starter has coincided with improved control. He improved his first-strike percentage from 55 percent to 59 percent and cut his walks per 9 from 3.7 to 2.6.
Harrison's history is that he wins without being overpowering. Last season, he averaged 5.6 strikeouts per 9 innings. That was the lowest strikeout rate for any of the pitchers who ranked in the top 30 in ERA last season.
Bud Norris Stats to Know
Norris had one of the most extreme home-road splits in baseball last season. He had a 1.71 ERA and 4.8-to-1 strikeout-to-walk ratio at home and a 6.94 ERA and 1.7-to-1 strikeout to walk ratio on the road.
One of the things that Norris did better at home last season was keeping the ball down. He threw 60 percent of his pitches to the lower half of the strike zone or below at home, compared to 55 percent on the road.
Norris allowed home runs on pitches located lower half or below once every 135 pitches last season. His upper half pitches were hit out at a rate of one for every 109.
Matchup to Watch: Adrian Beltre vs. Norris
Rangers third baseman Adrian Beltre hit 10 home runs off sliders last season, tied for the most in the American League.
Beltre's .600 slugging percentage in at-bats ending in a slider was the third-highest in the majors.
Norris threw his slider 36 percent of the time last season, the second-highest percentage of any pitcher who qualified for the ERA title.
Rangers' Rocky Finish
After being one of the best teams in baseball for most of the 2012 season, the Rangers limped to the finish line, eventually costing them the AL West title.
It was an across-the-board malaise. The team scored 5.2 runs per game from April to August, but only 4.3 in September and October. The starting pitchers ERA jumped from 4.22 to 4.66 and the bullpen ERA soared from 3.08 to 4.21.
The Rangers made some changes this offseason, trading Michael Young and watching Josh Hamilton sign with the Los Angeles Angels. This will be the first time since 2001 that Young was not in the Rangers Opening Day lineup.
Hamilton ranked third in the AL in OPS and fifth in home runs in his five seasons with the team.
The Rangers do have a recent history of starting well. They are 44-29 prior to May 1 over the last three seasons, the fourth-best record in the majors in that span.
Astros going to extremes with their budget
Not including the $5 million still owed to Wandy Rodriguez, the Astros opening day payroll is projected to be about $18.7 million.
The last team with an Opening Day roster whose players made less than $20 million was the 2006 Marlins ($15 million)
The team’s total payroll is just over $24 million, but $5.6 million is owed to players no longer with the team. That accounts for 23 percent of that $24 million.
There are 23 individual players (including four Yankees, four Dodgers and three Tigers) who will make more than the current Astros roster this season.
That $18.7 million is less than the Astros owed Carlos Lee at the beginning of 2012.
This year, Norris ($3 million) is the Astros’ highest paid player and he will make less than the league average.
Mark Simon and Jacob Nitzberg also contributed to this post.