According to CBS Sports' Jon Heyman, the free agent agreed to a three-year deal that likely would pay him more than $18 million. Heyman wrote that the deal wasn't finalized pending a physical. The report indicated that the St. Louis Cardinals also made a play for the 33-year-old veteran.
Affeldt made 10 postseason appearances this year, throwing 10 1/3 scoreless innings. He allowed just five hits and three walks (one intentional) while striking out 10.
Affeldt, Santiago Casilla and Sergio Romo combined to lock down the late innings for the Giants, as the bullpen continued to thrive in the absence of injured closer Brian Wilson.
In the regular season, Affeldt went 1-2 with three saves and a 2.70 ERA in 67 appearances.
Affeldt has a 2.73 ERA, a 10-9 record and 10 saves in four seasons with the Giants. He also was part of San Francisco's 2010 World Series title squad. Affeldt previously played for the Kansas City Royals, Colorado Rockies and Cincinnati Reds.
Two other key members of the Giants are free agents: second baseman Marco Scutaro, the NL Championship Series MVP, and center fielder Angel Pagan.