The Giants designated Clayton Tanner for assignment, according to Henry Schulman of the San Francisco Chronicle (on Twitter). The move opens up a 40-man roster spot for Eric Surkamp, who started against Houston tonight.
Tanner, a 23-year-old left-hander, has yet to appear in the Major Leagues. The 2006 third rounder has a 3.66 ERA with 6.6 K/9 and 3.0 BB/9 in 686 1/4 minor league innings. He has spent the 2011 season starting for the Giants' Double-A Richmond affiliate.