"I'm very excited to be in Boston and ready to beat the Yanks," he pronounced Monday.
The Red Sox completed their deal for the All-Star first baseman, acquiring the slugger from the San Diego Padres for three prospects and a player to be named.
"We're thrilled to be able to make this trade," Red Sox general manager Theo Epstein said.
"It makes them a great team. He's a heck of a hitter. That's a huge addition for Boston," Yankees general manager Brian Cashman said. "They just obviously improved themselves in a significant way. He's one of the premier players in that position in the game."
Gonzalez is entering the last year of his contract in 2011 and is due $6.3 million next year. Although the trade does not include a contract extension, Epstein said he's "confident" a contract will be worked out.
"We're going to try to get something so he will be here for a very long time," said John Boggs, Gonzalez's agent.
The absence of an announced extension could prompt calls to the commissioner's office - maybe from the New York Yankees - for an investigation. If an extension isn't formalized until after opening day, it wouldn't count against the Red Sox for the 2011 luxury tax.
In five seasons with San Diego, Gonzalez has 161 homers and 501 RBIs. Including parts of two seasons with Texas, he has 168 homers and 525 RBIs. He hit .298 with 31 homers and 101 RBIs last season.
Gonzalez's lefty swings put up big numbers despite him playing at pitcher-oriented Petco Park.
"I think he's going to be a monster in Fenway Park," Padres general manager Jed Hoyer said at baseball's winter meetings in Lake Buena Vista, Fla.
Epstein, too, predicts Gonzalez will quickly take aim at the Green Monster in left field.
"We think he is going to wear the wall out," Epstein said.
The Red Sox made a run at Gonzalez before the 2009 trading deadline and again last season, Epstein said. Gonzalez has been an All-Star the last three years and is two-time Gold Glover.
Hoyer, who previously worked for the Red Sox under Epstein, said the Padres were sure they wouldn't have been able to sign Gonzalez after next year. Rather than risk waiting for a deal next summer, Hoyer said San Diego decided to make a move now.
"There's plenty of examples of trades at the deadline where a team didn't get nearly what they thought they'd get simply because the market didn't develop or because of injuries," Hoyer said. "With that in mind, I felt like this was the right time to do it."
Hoyer said at least three teams were showing serious interest in getting Gonzalez. He said Epstein, his pal, had been "calling me more often than usual."
For the Red Sox, the trade allows them to play a little catch up with the Yankees. A couple of years ago, Boston was in the mix to sign star first baseman Mark Teixeira, who wound up going to New York.
Gonzalez had surgery to clean up the labrum in his non-throwing right shoulder on Oct. 20, but he said Monday he's ahead of schedule and expects to be ready for opening day.
"I'm very excited to start this new phase and look forward to a lot of world championships," he said.
Gonzalez, donning a Boston jersey without a number, said the Red Sox have always been his favorite American League team, in part because of Boston icon and Hall of Famer Ted Williams - like Gonzalez, Williams was a left-hander and San Diego native.
Epstein said the Red Sox had admired Gonzalez since his days as an up-and-coming player for the Texas Rangers.