UPDATE, 4:52 p.m.: Frandsen comments on the deal:
Frandsen's voice was breaking as he commented on the deal.
"I'm going from one class organization to another class organization," said Frandsen, who is the all-time hits leader at San Jose State. "I'm pretty lucky in that. You can hear it in my voice I'm kind of shocked. It's a little different knowing I came up in this organization. I'm going away and that's bittersweet.
"I'm pretty excited for the opportunity and that Boston wanted me. I'm sure I'll have a text in five minutes from Dustin."
The Giants will receive a player to be named later and/or cash.
Frandsen, 28, has a career slash line of .240/.304/.341 in 453 plate appearances in four seasons with San Francisco. Frandsen spent most of 2009 in Triple-A, hitting .295 with a .352 OBP in 110 games.
Frandsen has primarily played second base in his career, but has seen big league time at shortstop and third base. He also saw limited time in the outfield back in 2007. His defense is considered above-average at second base.
This move purely revolves around depth for the Red Sox. With Jed Lowrie hurt and other question marks regarding middle infielders, Frandsen may be a common name shipping up from Pawtucket this season. If Bill Hall also sees time out, Frandsen will be one of the first to get a nod to the big club.