They need him back to form in 2013, if they expect to challenge the Nationals and Braves in the National League East.
Halladay, who suffered through back and shoulder issues last season, threw 30 pitches in his first bullpen session of the offseason Tuesday, and general manager Ruben Amaro Jr. said it went well.
"He felt good about his mechanics," Amaro said. "[Pitching coach Rich Dubee] seemed to like what he saw. That's a good, positive sign. Obviously, we'll know more about how he's feeling once he gets out there and starts throwing more vigorous [bullpen sessions], but that's a good sign.
"I think more than anything else, he's right on schedule. He's on his planned throwing program. It was more just about how felt after he threw or while he threw. He said he felt better than he felt all spring last year, at least in the early part of the spring. That's good."
Halladay, 35, went 11-8 with a 4.49 ERA in 25 starts last season. It was his highest ERA since he had a 10.64 ERA in 2000.
Todd Zolecki is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.