The Astros continued their substantial rebuilding project by sending Pence and cash to the Phillies in exchange for four Minor League players, including Philadelphia's top two prospects -- pitcher Jarred Cosart and outfielder Jonathan Singleton. Houston also acquired relief pitcher Josh Zeid and a player to be named later.
Pence, easily the Astros' most popular player, was signaled by manager Brad Mills to come off the field in the middle of the fifth inning of Houston's 4-0 loss to the Brewers, when the teams had agreed on the deal. It was finalized not long after.
"It's been a long chapter," Pence said. "I've been with the Astros for a long time, and everyone knows I love all the guys here. I had a wonderful opportunity. The realization this day was going to come kind of hit me [Friday], and now it's a reality and ultimately it's going to be a win-win.
"The Astros are going to get some great players. It's a new chapter for them and a new chapter for me. I'm on board with a team that's got the best record in baseball and unbelievable talent. It's a wonderful thing for everybody."
By trading away their best player, the Astros continue to stockpile Minor League talent in an effort to rebuild a farm system that has been considered one of the weakest in the Major Leagues for the last couple of years. Houston traded starting second baseman Jeff Keppinger to the Giants for two Minor Leaguers on July 19.
Much of the Astros' premium young talent is at Double-A and below, and Houston tapped into that pool by calling up Double-A outfielder J.D. Martinez, their 2010 Minor League Player of the Year. He was hitting .340 with 13 homers and 71 RBIs in 87 games at Corpus Christi.
Martinez was removed from Friday's game in Midland in the third inning and told to pack his bags for Milwaukee, where he'll join the club Saturday.
"You put it on a pedestal your whole life, and when it actually happens you're in shock," Martinez told MLB.com. "I'm still freaked out."
Astros general manager Ed Wade said interest in Pence intensified in the last 24 to 48 hours prior to the trade as the Astros had ongoing discussions with several clubs.
"This is a bittersweet moment for us as an organization," Wade said. "Everybody connected with this organization takes pride in what Hunter Pence has done for us, the way he's come through the system and represented, not only our team but the city of Houston as admirably as he's done. Time and circumstance dictates that you have to do some tough things sometimes, and this certainly ranks among them."
Pence, 28, who was the Astros' top pick in the 2004 First-Year Player Draft, reached the Majors three years later and quickly became a fan favorite with his hard-nosed style of play. And when the Astros traded away pitcher Roy Oswalt -- a year ago Friday to the Phillies -- and Lance Berkman last July, Pence became the face of the franchise.
"I appreciate the love the fans have given me," Pence said. "It's been a wonderful time in Houston for me. I've had great memories and a great time playing for them. It's the only organization I've known. It was a good time, and I think there's going to be a bright future for both myself and the Astros organization."
Astros owner Drayton McLane, who is awaiting Major League Baseball approval to complete a sale of the team to a group led by Houston businessman Jim Crane, said the decision to trade away the popular Pence was done under his watch.
"We're still in charge, but they have clearly said they wanted us to strengthen our Minor Leagues," McLane said. "It was a heart-wrenching decision to trade Hunter, but because of his ability we were able to get four high-potential players."
Cosart, 21, grew up in the Houston area and was originally drafted by the Phillies in the 38th round in the 2008 First-Year Player Draft. He was 9-8 with a 3.92 ERA in 20 games (19 starts) at Class A Clearwater and will report to Corpus Christi.
"We view him as a top-of-the-rotation starting pitcher," Wade said. "He's at High A at this point in time, still a young developing player, but we felt that if we had a chance to get a top-of-the-rotation starter and a 30 home run guy in a deal like this, it made all the sense in the world. They were the two key pieces for us."
Singleton, 19, was hitting .282 with nine home runs and 47 RBIs in 92 games for Clearwater. A left-hander whom the Astros are listing as a first baseman and an outfielder, he will report to Class A Lancaster. He was taken in the eighth round by the Phillies in the 2009 First-Year Player Draft.
"We see him as a 30 home run guy in the big leagues," Wade said. "He's certainly one of the top prospects out there, one of Philadelphia's top prospects."
Zeid, 24, had a 2-3 record and a 5.65 ERA in 21 games, including 11 starts, for Double-A Reading this season. As a reliever, Zeid has a 2.25 ERA in 10 games. Originally a 10th round pick of the Phillies in 2009, he will report to Corpus Christi.
"Our scouts profile him as a back-end-of-the-bullpen player, at the very least a setup man with closer potential," Wade said.
The loss of Pence will leave a gaping hole in the Astros' lineup. Pence, the team's No. 3-hole hitter for most of the season, was leading the Astros in batting average (.308), home runs (11) and RBIs (62). His departure likely means immediate playing time for Martinez.
"Any time you lose a guy like Hunter, it's going to take something away from the lineup," Astros manager Brad Mills said. "Any ballclub, not just this one."
Wade, the former general manager of the Phillies, said Pence will fit in well with Philadelphia.
"I know how that personality's going to play out there in that market, and I think he's going to be very widely received there, and justifiably so," he said. "We're going to miss him. He's the kind of guy even us jaded people that get to see baseball games for free for 35 years would pay to see Hunter Pence play. We clearly recognize the magnitude of what this deal means is that regard."
Brian McTaggart is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.