One of those cornerstones was chipped away Friday when the Astros traded Pence to the Phillies in exchange for four players, including Philadelphia's top two Minor League prospects. Pence now has a chance to play for a World Series, while Bourn couldn't help but reflect on their time together.
"It was a great honor to play with him," he said. "He's a great teammate. Philly's getting a first-class player, a great addition to their team. You hate to see a teammate like that go. I've been playing with him since I came over here and we kind of grew up a little bit together, helped each other on the field. I wish him the best."
As the non-waiver Trade Deadline grew closer, Astros players became increasingly anxious about who was going to stay and who was going to leave. Rumors about Pence's departure filled the clubhouse on Thursday in St. Louis, and by Friday when the team arrived in Milwaukee it was clear something was going to happen.
Pence was in the lineup for the series opener against the Brewers, but was pulled out of the game in the middle of the fifth inning.
"It was crazy, it was awkward," third baseman Chris Johnson said. "I was sitting in the dugout and [manager Brad Mills] tells Jason Michaels to get his stuff because he was going to right field, and everybody knows why he was going to right field. Seeing Hunter running off the field was unbelievable to see. It will be hard to picture Hunter in another uniform. That's the business of the game, and we'll have to move forward."
Moving forward means the Astros are getting younger -- again.
Less than two weeks after trading away starting second baseman Jeff Keppinger to the Giants for a pair of Minor League pitchers, Houston's starting right fielder is gone. Jose Altuve was called up from Double-A to replace Keppinger, and the Astros called up 2010 Minor League Player of the Year J.D. Martinez to fill Pence's spot.
Bourn, one of the team's veterans and leaders, understands the direction the Astros are heading as they try to rebuild their farm system.
"I know they'll try to give us a team that's going to be able to win on the field," he said. "It might not make sense to us right away, but I know overall they're not going to put a team on the field that's not going to be able to compete with everybody on the opposite side. I think they'll continue to build and get us the pieces we need to compete in the NL Central."
Bourn, who was drafted by the Phillies before being traded to Houston in 2007 in the Brad Lidge deal, was thrilled to see Pence have a chance to reach the playoffs.
"At least he's going to an organization where he'll be well-taken care of," he said. "You hate to see him leave. He played with desire and left his heart on the field each and every day. He always left it on the field. I'm a competitor, also, and when we competed against each other, we'd go head-to-head in whatever it is."
Johnson was a part of the nucleus last year that included four everyday rookies after Lance Berkman was traded, joining first baseman Brett Wallace, catcher Jason Castro and the shortstop combination of Tommy Manzella and Angel Sanchez.
The club flourished in the second half of the season, and Johnson says the young players need to step up again.
"We're going to have to carry the load," he said. "It's a big weight that Hunter is leaving, so somebody is going to have to pick it up and try to run with it, and that's what we're going to have to do starting [Saturday]."
Mills said Pence will be missed in many ways.
"Everybody has a lot of heart for Hunter and everything he's meant to this organization, and everything he's done for the fans and baseball and everything else," he said. "He's a special guy and a special player, and I know that he'll do well there."
Brian McTaggart is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.