According to various sources the San Diego Padres have agreed to deal 1B Adrian Gonzalez to the Boston Red Sox for Casey Kelly, Anthony Rizzo and Reymond Fuentes.

According to ESPN Boston's Gordon Edes, Theo Epstein flew from San Diego to Boston with Adrian Gonzalez.

The Red Sox have received permission from Major League Baseball to negotiate with Gonzalez on a new contract, sources told ESPNs Buster Oleny, and Gonzalez's physical examination, one of the last hurdles to the deal, could happen Saturday. The team already has flown in Gonzalez.

Kelly, 21, is considered the top prospect in the Red Sox organization by Baseball America, though he struggled a bit in his first season at Double-A in 2010. He was 3-5 with a 5.31 ERA in 21 starts for the Portland Sea Dogs, and had a 6.75 ERA in four starts in the Arizona Fall League recently.

Rizzo, also 21, had 20 homers and 80 RBIs with the Sea Dogs this past season and had an .815 OPS. He was ranked the No. 3 Red Sox prospect by Baseball America.

The 19-year-old Fuentes was Boston's top pick in the 2009 draft. He hit .270 with 59 runs scored and 42 stolen bases in 104 games for Class A Greenville last season. He's ranked the No. 6 Red Sox prospect by Baseball America.

The trade for Gonzalez almost assuredly means that Adrian Beltre will not be returning with the Red Sox and his best offer is currently with the Athletics.