Manager Rob Thomson said Thursday that Walker will work out of the bullpen going forward, Todd Zolecki of MLB.com reports.
After surrendering six earned runs on 13 hits and a walk without recording a strikeout in six innings against the Astros on Wednesday, Walker has now officially lost his place in the Phillies' rotation. He'll serve as a long reliever as he joins Philly's bullpen, and the team will need to recall someone -- likely Tyler Phillips -- from Triple-A to fill the open rotation spot, which is due to pitch in Toronto on Tuesday.