The long-discussed deal swaps a proven pitcher for two highly talented pitchers -- Hirsh, the key to the deal, was chosen Pitcher of the Year in the Triple-A Pacific Coast League last season and the Double-A Texas League the previous season, and Buchholz has greater fastball velocity than Hirsh.
For a team that wants to win with young players, O'Dowd will take that.
"We were very fortunate to work this deal out," O'Dowd said. "When I talked to Jason, I told him that this had nothing to do with his contract. We would have made this trade at any point in time.
"This trade gives us more flexibility as we continue putting our club together, and I think it's going to make us a better club next year and in the future."
Hirsh, who was the Astros' top pick in 2003 and turns 25 on Feb. 20, went 13-2 with a 2.10 ERA in 23 starts for Triple-A Round Rock. He also went 3-4 with a 6.04 ERA in the first nine starts of his career, with the Astros.
In 2005, he was touted as the Astros organization's top prospect as he went 13-8 with a 2.87 ERA at Double-A Corpus Christi.
"He's 6-8 and 260 pounds, with very good control, a high-average Major League fastball and two secondary pitches that he's still working on," O'Dowd said. "He still has a significant ceiling."
Buchholz, 25, went 6-10 with a 5.89 ERA in 22 games, including 19 starts, for the Astros as a rookie in 2006. He also made seven appearances at Round Rock. Buchholz suffered from shoulder problems in 2004 and had just 20 starts in 2005.
"He already has a full year at the Major League level and has a better arm than Hirsh -- 92-96 [mph] on his fastball," O'Dowd said. "He's got a good breaking ball from top to bottom. He has to show more durability."
Buchholz originally was a sixth-round pick of the Phillies in 2000. The Astros acquired Buchholz and fellow pitchers Brandon Duckworth and Ezequiel Astacio from the Phillies for closer Billy Wagner.
The pair could be competing for the same spot in the starting rotation, which returns Aaron Cook, Jeff Francis, Byung-Hyun Kim and Josh Fogg, who was tendered a contract offer Tuesday.
Taveras, who turns 25 on Christmas Day, has a .284 average and 68 stolen bases in 311 career games. What's not clear is whether the Rockies will use his speed to cover the expansive ground at Coors Field and provide speed at the top of the order, or if they'll deal Taveras to fill other holes. The Rockies continue to look for a center fielder in the free-agent market and could choose to go with a hitter with more power than Taveras.
Taveras batted .278 with 33 steals, one home run and 30 RBIs in 2006. He also hit .349 during a 30-game hitting streak that was the second-longest in the Majors last season (the Phillies' Chase Utley went 35 games) and longest by five games in Astros history.
O'Dowd noted that Taveras is a player with high-end speed, and "there are very few of those in the game."
Last season, Jennings had the second-lowest run support in the Majors and went 9-13 with a .378 ERA. Now he will pitch 186 miles from Baylor University, where he played collegiate ball and earned collegiate player of the year honors in 1999.
"It's definitely mixed emotions," Jennings said. "I'm excited to go to a good ballclub, a team that has playoff aspirations every year, which is something I've yet to experience. At the same time, I've been with Colorado my whole career, so [we have] a lot of good relationships up there, we have family up there.
"It's definitely a business and I understand that, and I'm looking forward to a new opportunity with a new team. It's almost like a breath of fresh air, a whole new beginning for me."