Walker will draw the start for the Phillies' series opener against the Mets on Thursday, Todd Zolecki of MLB.com reports.
Walker was relegated to the bullpen following his last start against the Astros on Aug. 28, when he allowed six runs on 13 hits and one walk over six innings. He allowed five runs (four earned) across his first two relief outings, but after Walker tossed three scoreless innings against the Mets on Saturday, manager Rob Thompson has decided to give the 32-year-old right-hander another look as the club's No. 5 starter. Overall, Walker holds a 6.29 ERA, 1.63 WHIP and 55:31 K:BB across 78.2 innings this season.