Walker allowed four earned runs on four hits while failing to record an out in Wednesday's 6-4 win over the Diamondbacks.
Walker entered in the eighth inning and gave up three singles and a double before being pulled. The right-hander has surrendered six runs over 1.2 innings in his last three appearances, totaling 42 pitches during that span. He now owns a 7.06 ERA, 1.75 WHIP and 18:12 K:BB across 21.2 innings in 24 outings this season.