Jennings, 28, was 9-13 with a 3.78 ERA for the Rockies in 2006 with three complete games and two shutouts. Colorado's all-time leader in victories, Jennings' 3.78 ERA last season represented the second-lowest full-season mark in Colorado franchise history and ranked 12th overall in the National League. Jennings also posted career-high totals in 2006 in innings pitched (212) and strikeouts (142).
"This is obviously a big piece of our puzzle that we tried to solve all offseason, to get that solid No. 2 starter and put him in our rotation," Purpura said. "Jennings has been very impressive. Last year we watched him very closely, from May 29 to the end of the season his ERA was only 3.17, the second-lowest in the NL during that time and fourth in the Majors.
"He had three complete games, two shutouts during that period, plus he had the second-lowest run support in the Major Leagues during that period of time. We certainly think that now with our lineup with Carlos Lee and Lance Berkman and some of our other [hitters], that certainly he'll benefit from the fact that he'll have much better run support to look forward to."
From May 29 until end of the 2006 season, Jennings' 3.17 ERA trailed only Johan Santana (2.44) of Minnesota, new teammate Roy Oswalt (2.78), and Erik Bedard (2.91) of Baltimore.
Jennings, who is signed through the 2007 season for $5.5 million, is eligible for free agency next winter and had been seeking a contract extension with the Rockies. Purpura said the Astros hadn't discussed an extension with Jennings yet and Jennings said he hadn't thought about his contract since hearing the news that he'd been traded.
"It's definitely mixed emotions, 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," Jennings said. "At the same time, I've been with Colorado my whole career, so 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."
In 156 career starts from 2001-06, Jennings was 58-56 with a 4.74 ERA, including six complete games and three shutouts. He was the 2002 National League Rookie of the Year after finishing 16-8 that season with a 4.52 ERA in 32 starts.
Jennings didn't come cheaply.
Taveras was runner-up to Ryan Howard in the Rookie of the Year voting in 2005. Hirsh, a former No. 1 pick and the Pacific Coast League and Pitcher of the Year last season, was expected to compete for spots in Houston's rotation next spring along with Buchholz.
"Certainly, you have to give up talent to get talent. We have a saying in our group that a trade isn't a good one unless it hurts both sides -- certainly, this does," Purpura said. "We lose Willy T., whom everyone loves. To me, that's the hard part of this situation. I love Willy Taveras, I think he was a wonderful part of our ballclub, but I think we're better offensively with Chris Burke in center field. I'm absolutely convinced of that. Obviously, Chris hasn't played the position on a full-time basis, but now this opens up an opportunity."
If Burke falters, Jason Lane, who is working out as a center fielder in Venezuela this winter, could get a chance in center. The Astros signed Lee to play left field and have Luke Scott, who hit .336 in 63 games following his recall after the All-Star break, to start in right field.
"Chris Burke, this opens up a position for him to play every day," Purpura said. "This is a situation where we got that solid No. 2 starter [and] depth in the bullpen. Willy T., we felt like he somebody we could move because we have Hunter Pence coming. I expect he'll get a chance to make his Major League debut next year."
Asencio, 26, was 1-0 with a 4.70 ERA in three games for the Rockies last season and 8-7 with a 5.03 ERA in 38 games, including 16 starts, for Triple-A Colorado Springs. In 42 career Major League appearances (30 starts) with Kansas City (2002-03) and the Rockies (2006), Asencio is 7-8 with a 5.12 ERA.
Purpura views Asencio as another power right-handed arm to complement Dan Wheeler, Chad Qualls and Brad Lidge in the Houston bullpen.
"He's got a very good arm," Purpura said. "He had Tommy John surgery in 2004, missed all of '04 and '05, came back last year and threw over 100 innings. Our scouts had him [throwing at] 92-94 miles per hour. He's a high velocity type guy [and] gives us another quality arm to the bullpen."
Jennings is expected to step into the No. 2 spot in the rotation behind Oswalt and ahead of right-hander Woody Williams, with lefty Wandy Rodriguez, Ezequiel Astacio, Matt Albers, Fernando Nieve and Chris Sampson battling for the other two spots, assuming Roger Clemens doesn't take one of them. Purpura had nothing new to report on the latter's situation.
Jennings could prove to be an upgrade over Pettitte, at least as far as the 2007 season.
Jennings is six years younger than Pettitte, he worked 212 innings last season and 535 over the last three seasons. Over the last five seasons, Jennings has been a workhorse, averaging 188 innings per year.
Like Pettitte, Jennings is a pitcher who induces a lot of ground balls and excels with a good defense behind him. Unlike Pettitte, Jennings hasn't had much success at Minute Maid Park. Jennings is 0-3 with a 10.47 ERA in three career starts at the Astros' home park.
But Jennings solved Coors Field, and the Astros don't believe Minute Maid Park will be a problem for him.
"One of the things that [Astros manager] Phil [Garner] and I really like about him is he's a sinkerballer," Purpura said. "He's had the most wins in Rockies history [and] the most wins in Coors Field, which is a feat in itself."
Jim Molony is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.