ATLANTA — Tom Glavine’s outlook on his season is improving with the health of his left shoulder.

Only three weeks after he spoke of possible retirement, Glavine said Monday he felt no pain in his first time throwing off a mound since inflammation was found in his left rotator cuff last month.

Glavine threw for about 15 minutes in the Atlanta Braves bullpen before Monday night’s game against the New York Mets.

"That side session today was better than any side session I had in spring training," he said.

Glavine said he wasn’t "trying to do anything spectacular the first time" but said he was able to throw "without any pain inhibiting me from doing what I wanted to be doing."

On April 14, Glavine said he might retire if pain continued in the left shoulder. He has been encouraged by his recent ability to throw in the outfield on back-to-back days, and he was upbeat after his first return to the bullpen.

"I’m encouraged by it," he said. "Again I think my biggest concern was going out there today and being able to go through my windup and make pitches the way I want to make them. ... I accomplished that."

The 43-year-old Glavine, who has 305 career wins, said he plans to throw another side session on Friday and continue to build arm strength before planning what he hopes will be only one or two minor league rehab starts.

Glavine was projected to open the season as the team’s No. 5 starter before experiencing shoulder pain.

The left-hander was 2-4 with a 5.54 ERA in 13 starts last season. He had offseason operations on his left elbow and shoulder.

The procedure on the elbow was believed to be more serious, but discomfort and weakness in Glavine’s shoulder led Dr. James Andrews to advise last month that Glavine rest the shoulder for two weeks.

Glavine said he already has renewed confidence in the shoulder.

"Certainly there’s plenty more room for building up arm strength and all that stuff, but as far as location and feeling good on all my pitches, my stuff was good and most importantly I didn’t throw any pitches that hurt or made me feel like I didn’t want to do that again," he said.

Braves manager Bobby Cox kept an eye on Glavine’s work on a dugout monitor.

"He was lights out," Cox said.