The Red Sox have agreed to a deal with the Padres to trade first baseman Adrian Gonzalez for three prospects, according to ESPN.
Sources told ESPN that Boston received permission from Major League Baseball to negotiate with Gonzalez.
Gonzalez flew to Boston to take a physical exam needed to complete the trade, a person familiar with the situation told The Associated Press on Saturday.
The Padres would receive three prospects in pitcher Casey Kelly, first baseman Anthony Rizzo and outfielder Reymond Fuentes, a baseball source told ESPN.
Gonzalez had surgery to clean up the labrum in his non-throwing right shoulder on Oct. 20. The Padres said then that the three-time All-Star and two-time Gold Glove Award-winning first baseman was expected to be ready for spring training.
The popular Gonzalez grew up in the San Diego area and was the No. 1 overall pick by Florida in the 2000 amateur draft. He was obtained in a trade with Texas before the 2006 season and has blossomed into one of the game's best first basemen. The left-hander hit .298 with 31 homers and 101 RBIs last season.
Boston was interested in Gonzalez last winter.
While many had expected Gonzalez to be traded before the deadline last summer, the Padres were surprise contenders in the NL West and had to keep the slugger.
The Padres went 90-72 despite opening the season with a payroll of $37.8 million, second-lowest in the majors. San Diego was in contention until the final day, when its loss at San Francisco, coupled with Atlanta's win over Philadelphia, eliminated the Padres from the NL West and wild-card races.
Hoyer has said for some time that the Padres wouldn't be able to afford the kind of big-money contract Gonzalez would command if he hit the free-agent market.
Hoyer also has said he anticipated Gonzalez being on the opening-day roster. But the allure of prospects is probably too much to pass up for a team that anticipates a player payroll of approximately $40 million.
The Padres recently exercised Gonzalez's $6.2 million option for 2011, the final year of a team-friendly $15 million, five-year contract he signed in 2007.
In five seasons with San Diego, Gonzalez has 161 homers -- two shy of Nate Colbert's club record -- and 501 RBIs. Including parts of two seasons with Texas, he has 168 homers and 525 RBIs.
He set a Padres record with his fourth 30-homer season. His third 100-RBI season tied Phil Nevin for the most in club history.
The Padres already have lost right-hander Jon Garland, shortstop Miguel Tejada and catcher Yorvit Torrealba to free agency, and won't re-sign outfielders Scott Hairston and Tony Gwynn Jr. They also declined to pick up right-hander Chris Young's $8.5 million option.