Giants manager Tony Vitello said on KNBR 680 that Walker will be optioned to Triple-A Sacramento prior to Thursday's contest versus the Rockies.
He'll clear off the roster to make a spot for Carson Whisenhunt, who is slated to make a spot start Thursday. Walker was unscored upon in his first five appearances after returning from a stint in the minors, but the former closer has since allowed 11 runs across his last 6.1 innings.