PHOENIX -- Less than a month ago, Henry Sosa was in the process of making the transition toward becoming a starter at the Double-A level with the Giants, a team stocked with solid Major League arms. The big leagues seemed a world away.
The Astros, who have proved to be the land of opportunity for young players in the past few weeks, acquired Sosa in a trade with the Giants for veteran Jeff Keppinger on July 19, with general manager Ed Wade saying he would compete for a spot in the rotation in 2012.
Sosa made his Major League debut much sooner than expected and showed some promise.
The 26-year-old right-hander threw six innings and allowed six hits and four runs -- three of which came in the first inning -- and suffered the loss in a 6-3 setback to the D-backs on Wednesday night at Chase Field.
"I thought he had to find some things in the first inning and made some real good adjustments," Astros manager Brad Mills said. "He threw the ball really well after that. In the fifth inning, he gave up those two doubles for the fourth run, but at the same time we saw a guy with a pretty good arm and some pretty good stuff, and I liked the way he was able to find himself and come back."
So much so the Astros plan to keep him in the rotation for the near the future, leaving him in the spot that had been occupied by J.A. Happ before he was sent to Triple-A Oklahoma City last week. Sosa had made three starts at Double-A Corpus Christi and just one start for Oklahoma City before the Astros called him up late Tuesday.
He settled down after his rocky first inning and held the D-backs to one run in his final five innings and flashed a big grin at reporters after the game. He had a lively fastball and much better control as the game progressed.
"I felt great," he said. "I think the first inning I overthrew the ball a little bit, but later on I felt I could do the job."
Sosa, who made the drive from Tucson to Phoenix earlier in the day, gave up a home run to Willie Bloomquist on the fourth pitch he threw. Paul Goldschmidt had a two-run single later in the inning to put Arizona ahead, 3-0.
"After the first inning, I said, 'Hey, it's not over. You're still going to go out there and pitch,' and he did," Mills said. "He made some adjustments with a few things and worked all the way through."
Sosa held the D-backs to one hit in the next three innings before doubles by Justin Upon and Chris Young scored a run and gave Arizona a 4-2 lead in the fifth. He threw 62 of his 100 pitches for strikes, with 27 of those pitches coming in the first inning.
"I slowed down because at the beginning was too fast," he said. "When I slowed down, I threw more strikes because my pitches were moving better -- command of fastball and the slider."
The Astros didn't manage their first hit against Arizona starter Josh Collmenter (7-7) until Brian Bogusevic led off the fifth with a single. Jimmy Paredes followed with a double into right field, putting runners at second and third with no outs.
Clint Barmes' bloop single scored Bogusevic, and Humberto Quintero dropped an RBI single into right field to score Paredes and extend his career-long hitting streak to 10 games. The Astros trailed by one run but would get no closer.
"It's picking up his ball," Barmes said of the challenge of facing Collmenter. "He gets to the top of the strike zone and he's got a good plane out of his hand to the catcher. All of us really battled to get on top of him, and he was beating us with his fastball a lot of the times. That was our big battle and we were able to have one big inning, but it just wasn't big enough."
Collmenter has thrown at least five innings 12 times this year, tying him with the Astros' Jordan Lyles and Philadelphia's Vance Worley for the third most among National League rookies. Only the Mets' Dillon Gee and the Braves' Brandon Beachy have done it more times in 2011.
"He moved the ball in and out much better tonight, he elevated tonight and we hit our spots much better tonight," Arizona manager Kirk Gibson said. "Those guys are still very aggressive. If you leave it out in the middle of the plate, they get after it."
The D-backs scored an unearned run in the seventh off Wilton Lopez and got an RBI triple from Gerardo Parra in the eighth off Aneury Rodriguez to take a 6-3 lead.
The Astros had the bases loaded with one out in the eighth inning but managed only one run when Carlos Lee grounded out. Houston went down in order in the ninth.
"We scored a couple of runs and we had a couple of other guys on with an opportunity to do it," Mills said.
The loss dropped the Astros (38-79) to 41 games under .500 for the first time in their history.
Brian McTaggart is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.