Walker (knee) is on track for either live batting practice or possibly a game Monday, Scott Lauber of The Philadelphia Inquirer reports.
Coming back from right knee soreness, Walker will throw another bullpen session Friday and, if that goes well, will face hitters in some fashion Monday. The veteran right-hander should still have time to ramp up for his spot in the Opening Day rotation, but he can't afford any more bumps in the road.