Walker allowed two hits while striking out one in a scoreless inning during Thursday's 6-1 win over Arizona.
Walker struggled during his previous stint in the big leagues, but he was recalled from Triple-A Sacramento on Monday and hasn't surrendered a run in any of his three appearances since. The 30-year-old right-hander has allowed four hits and one walk while striking out three in 3.2 innings over that three-game stretch. Overall, he owns a 6.60 ERA, 1.77 WHIP and 22:16 K:BB across 30 innings with San Francisco this season.