The 21-year-old, 5-foot-7 Altuve led the Minor Leagues with a combined .389 batting average between Class A Lancaster and Corpus Christi. He hit .408 in 52 games at Lancaster before joining Corpus Christi, where he hit .361 in 35 games.
"It's pretty exciting to see a guy with a lot of energy and a lot of range, a guy who is having a real good year in Jose Altuve, come up here," Mills said. "Change is inevitable. It's going to happen, and it's nice to make a change with the guys we have."
Altuve had originally slotted in the Hooks' lineup before finding out from general manager Ed Wade that he had to can a flight to Houston.
"I was in the middle of [batting] practice," said Altuve, "then they called me out, and they put me on the phone with the general manager, and he told me, 'Hey, Jose, how do you feel?' I said, 'I feel good,' and he told me, 'OK, because you're ready to go to the big leagues.' I was like, 'Wow.' That was a good moment right there."
Altuve combined to hit 22 doubles, 10 triples and 10 home runs in 2011 while stealing 24 bases and knocking in 59 runs. He was signed as a non-drafted free agent by Houston out of Venezuela in September 2006.
"Everybody is going to see Jose and see his stature, and begin to question his ability from there," Wade said. "In that case, people are really going to underestimate what this kid is all about. He's got a chance to be a really good big league player."
Altuve represented the Astros in the 2011 Futures Game and notched two hits.
Both pitchers acquired from San Francisco were playing for Double-A Richmond at the time of the trade. Sosa, 25, is a right-handed starter who split the season between Richmond and Triple-A Fresno. He had a 5-2 record and 2.68 ERA in eight games at Richmond, and combined to post an 8-3 record with a 5.51 ERA between the two teams.
"We think this Sosa kid has a chance to pitch in our rotation, possibly next year," Wade said.
Stoffel, 22, is a right-handed reliever who recorded a 3.98 ERA with 13 saves in 32 games at Richmond. The Arizona product was drafted by the Giants in the fourth round of the 2009 First-Year Player Draft.
"This is a deal that we felt, at this point in time, made sense for us if we can get some prospect depth in this system," Wade said. "We like both these arms, and it gives us the type of depth at Double-A ... that can conceivably make them two pitchers who can show up here in the short term and provide us with some help."
This is the fifth time Keppinger has been traded in his career. The Astros had a deal in place to trade him to the Yankees in the offseason before an injury to his foot dismantled the deal.
"It's definitely a good situation," Keppinger said. "If you're getting traded, that's probably the main situation you want to go to. You want to go to a team that's in contention. I know going to San Fran, they pack out just about every game."
Keppinger is excited about the trade and thankful to have played for Houston, where he found consistent playing time for the first time in his career.
"Ed told me they would like me to be there by game time tomorrow, which I just found out was a day game, so it's going to be a little tough," he said. "But you've got to do what you've got to do."
Keppinger had been slotted to start at second base for the Astros on Tuesday; Angel Sanchez took his place.