CHICAGO -- The Cubs moved a step closer to getting starter John Lackey back after the veteran righty threw a bullpen session Monday at Wrigley Field without incident.

The session went "quite well," according to a Cubs official. If Lackey does not experience any unexpected soreness when he reports to the park Tuesday, he'll be slated for a second bullpen session later in the week. If that goes well, he'll likely be activated to resume his turn in the Cubs' rotation.

Lackey, 37, has been on the 15-day disabled list since Aug. 15 because of a right shoulder strain. The decision to put him on the DL was largely viewed as precautionary for the front-running Cubs, who are nursing a big lead in the National League Central.

Lackey is 9-7 with a 3.41 ERA for Chicago in his 14th big league season. He hasn't pitched since Aug. 14, when he left a start against St. Louis in the seventh inning because of shoulder tightness.

"We'll know after this one and the next [bullpen session] where he's at," Maddon said before Monday's game. "But he's doing well. No setbacks or complaints on his part or the trainer's part. Everything is in pretty good shape, it looks like."