In addition to LaRoche, the Pirates will receive Minor League outfielder Jamie Romak, with shortstop prospect Brent Lillibridge heading to Atlanta.
By acquiring LaRoche, the Pirates fulfill their primary offseason objective of landing a young, left-handed power bat for the middle of their lineup. LaRoche, 27, batted .285 with 32 home runs, 90 RBIs and an OPS of .915 last year in his third season with the Braves.
Gonzalez, 28, went 3-4 with a 2.17 ERA and converted each of his 24 save opportunities last year in his first season as a closer. There had been some concerns on the Braves' part about Gonzalez's health, because the hard-throwing southpaw was sidelined for the final month of the 2006 season with a sore left elbow.
Gonzalez, in a telephone conversation with MLB.com on Wednesday night, said that he felt mixed emotions about the deal.
"Of course, I'm very pleased to be going to a great team like the Braves. They're a powerhouse," said Gonzalez. "But then again, I have my teammates in Pittsburgh that I've grown fond of. This is really the only organization I know.
"I'm happy for both sides. The Pirates are going to be a good team in the coming year. But now I'm going over there, and I'm ecstatic to get things going with the Braves."
The Gonzalez-for-LaRoche deal was nearly consummated during the Winter Meetings in December, but the Braves backed out when the Pirates would not add a second player to go along with Gonzalez. The two teams had remained in contact throughout the past month in an effort to come up with a transaction that was satisfactory for both sides.
There could be a financial motivation behind the Braves' decision to pull the trigger on the deal. On Tuesday, the Pirates signed Gonzalez to a one-year deal worth $2.35 million, thus avoiding the arbitration process. The Braves could not agree to terms with LaRoche before the Tuesday deadline for teams to exchange salary figures with arbitration-eligible players. Atlanta made an offer of $2.8 million to LaRoche, who is seeking $3.7 million.
Romak, 21, could add some much-needed additional power to the Pirates' farm system. The right-handed hitter batted .247 with 26 doubles, two triples, 16 home runs, 68 RBIs and an OPS of .840 in 348 at-bats with Class A Rome last season.
Lillibridge, 23, combined to hit .305 with 13 home runs, 71 RBIs and 53 stolen bases in 2006 while splitting the season between low Class A Hickory and high Class A Lynchburg.
Ed Eagle is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.