To put LaRoche in the Red Sox uniform that he will first wear on Friday night at Fenway Park against the Orioles, Epstein merely had to part with two Minor Leaguers -- shortstop Argenis Diaz and right-hander Hunter Strickland. Neither player had been viewed as a key piece of Boston's future, which made the trade one that Epstein couldn't turn down.
"We've been in the market for a player who could do some damage against right-handed pitching and help our club's depth at the corner infield," said Epstein. "We've checked in on a number of players that fit that category and found that -- by a large, large margin -- the Pirates had the most reasonable acquisition cost.
"This was a chance to get -- at a very reasonable acquisition cost -- a player that we think will help our club against right-handed pitching and add to our depth and leave us in a position to continue to look for more impact before the end of the Trading Deadline."
A starter for the Pirates, LaRoche, who is hitting .247 with 12 homers and 40 RBIs, will likely come off the bench in Boston. But he figures to get plenty of chances to play for Red Sox manager Terry Francona, who is adept at utilizing his entire bench.
"There's some uncertainty with our health, and I think there's some concern in the organization about enough depth, where if something does happen, where do we go?" Francona said. "And so in the meantime, it seems like we have extra players, which is something I need to deal with and communicate and do a good job and make it work really well."
Francona and Epstein will sit down during the team's off-day in Boston on Thursday and determine not only a corresponding roster move to make room for the newest member of the Red Sox, but also a rough outline of how LaRoche will be used.
The addition of LaRoche means that third baseman Mike Lowell can rest his surgically repaired right hip more often. Kevin Youkilis, Boston's All-Star first baseman, can move to third on days Lowell doesn't play, creating a slot for LaRoche.
"I think we're trying to add some depth to the team, some power from the left side and I would assume versatility," said Lowell. "How it's going to affect me? We'll see. We're going to try to put the best team out there to win, so whoever that is is going to be playing. I don't have a crystal ball, so I have no idea how it's going to play out."
LaRoche will see plenty of familiar faces when he gets to Fenway on Friday. Among his former teammates are John Smoltz, Jason Bay, Nick Green and J.D. Drew.
"I can think of a lot worse places to go," LaRoche told reporters in Pittsburgh. "It's nice to be back in the hunt with somebody. I've missed that. When I was in Atlanta, I was lucky enough to be in the postseason and games in September that counted. That's going to be a blast. There are a few guys over there I've played with. Again, it's going to be a blast."
Smoltz is looking forward to the reunion.
"He's got one of the best swings in the game," said Smoltz, who teamed with LaRoche on the Braves for three seasons. "Hopefully, he can continue what he's been doing in an atmosphere he's not been used to in a while. He's one of the best guys in the world. He's an extremely interesting guy, the way he goes about his business and does his thing. Very unassuming, and he's got one of the best [set of] hands for a first baseman you'll see. We had a lot of fun together."
The timing could be just about perfect for the move, as LaRoche has been a second-half force through most of his career.
"The big second-half numbers are nice," Epstein said. "I don't think we go so far as to say they're definitely predictive, so I don't think we would ever make a trade based on a player's first-half or second-half splits. But it does provide some reason for optimism."
Bay, who played with LaRoche as recently as last season with the Pirates, predicts his friend will thrive in Boston.
"Good teammate, good hitter, good first baseman," said Bay. "It's been noted that he gets off to slow starts, so we're kind of picking him up on the upswing. He always has a good second half. All-around, he's a good guy to have around."
Though going from a small market to a big one is often a tough adjustment for a player to make, Bay thinks that LaRoche's personality will make it just about seamless.
"I think he'll take it fine," Bay said. "You'll find out when you meet him. He's one of a kind. He's a great guy. He's a country boy. He kind of takes things very slow. He moves in slow motion almost. Nothing really fazes him."
The Red Sox have been in a team-wide slump of late, so that -- while not the impetus for the trade -- only enhanced Epstein's reasons for pulling the trigger.
"He's a left-handed first baseman with some pop in his bat and plays a smooth first base," said Bay. "He's got a little thunder. Offensively, we've struggled a little bit lately. Hopefully, the last two months of the season, he can add some power to the lineup."
It remains to be seen how all the pieces will fit together. The Red Sox already have a left-handed backup at first base in Mark Kotsay, but he also plays the outfield.
Lowell was activated from the disabled list on July 17 following a 19-day break. The veteran third baseman is hitting .289 with 10 homers and 42 RBIs over 72 games.
LaRoche, 29, is eligible for free agency at the end of the season. A potential "Type B" free agent, the Red Sox could receive Draft compensation if he signs with another team.
"It wasn't a key component in the decision. I think we recognize that it's far from a certainty, but if he does have his characteristic big second half, there's a chance he would obtain that status," Epstein said. "Under some scenarios, it could yield the club a Draft pick. It's certainly not something that was counted on. I think he was acquired primarily to help the 2009 Red Sox and help our ability to hit right-handed pitching and to provide needed depth to our position-player base and our corner infield."
LaRoche is a career .269 hitter with 123 homers and 426 RBIs in 775 games.
In Diaz, the Pirates gained a potential elite defender. Playing for Double-A Portland this season, Diaz hit .253 with no homers, 24 RBIs and seven stolen bases.
Strickland was selected by the Red Sox in the 18th round of the 2007 First-Year Player Draft. Listed at 6-foot-5 and 200 pounds, Strickland was 5-4 with a 3.35 ERA for Class A Greenville this season.
Meanwhile, Epstein will continue to explore other opportunities to improve the team with just over a week remaining before the July 31 non-waiver Trade Deadline.
"One of the things that we liked about today's acquisition is that it was at a relatively reasonable acquisition cost, especially in terms of our prospect inventory, so that there's no real opportunity cost lost with this move," Epstein said. "We'll still continue to pursue further upgrades to the club."
Ian Browne is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.