Greg Dobbs hit a two-out single to left to score John Mayberry, Jr. in the ninth inning to lift the Phillies to the win.
The 29-year-old Myers, who spent eight seasons with the Phillies, was replaced by Chris Sampson after facing one batter in the sixth inning. Myers was hurt while covering first base when Philadelphia first baseman Ross Gload grounded out to open the sixth.
Myers, who will be reevaluated Friday, doesn't expect to miss his next start.
"I felt something, and I learned from previous muscle stuff to not push it again," said Myers, who allowed three runs on seven hits in 5 1-3 innings. "I gave it one throw and felt it a little bit and thought, `It's not worth it.' If I did keep going, I could have (been out) a month instead of like three days."
Plagued by injuries in his final season with the Phillies last year, Myers doesn't believe the groin injury was anything that would set him back with the regular season looming.
"Not at all," Myers said. "It wasn't painful enough to where I was like `Oh, this could be something serious.' I knew it was kind of minor, and I didn't want to risk it because we're so close to the season. It could be a week, but I don't know. We'll see how it feels tomorrow."
The Phillies' first-round pick in the 1999 draft, Myers was the team's Opening Day starter in each of the last three years. Myers was 73-63 with a 4.40 ERA and 21 saves in eight seasons with the Phillies. He missed most of 2009 after undergoing hip surgery in June. Shortly after the season ended, the Phillies announced that they would not pursue him as a free agent.
"They were good to me," Myers said. "(Now) they're like my stepbrother, and you usually don't like your stepbrothers when you're playing against them. But they've been my family for a long time and I don't have anything bad to say about them or the organization. They took care of me. I pretty much grew up in the organization."
Besides pitching against his former team for the first time, Myers also got the chance to hit off former teammate and friend Kyle Kendrick. Myers reached on an infield single in his first at-bat.
Kendrick kept his name in the minds of the coaching staff and management as he continues to compete for the fifth starter's job. The 25-year-old right-hander allowed two runs - one earned - in 5 2-3 innings.
"Obviously, you want to hear something, but it'll come down to the wire," Kendrick said. "They don't have to make a decision now. Like I've said before and like I've said all spring, it's out of my hands."
Kendrick is competing with 47-year-old Jamie Moyer for the final spot in the rotation. Moyer is scheduled to start Friday night when the Phillies travel to Tampa to take on the New York Yankees.
NOTES: Philadelphia RHP Roy Halladay pitched seven sharp innings in a minor league game against the Yankees' farm team in Tampa on Thursday. Halladay allowed two runs on seven hits while striking out seven and walking one. Halladay, who threw 99 pitches, is expected to make one more start before his Phillies' debut on April 5 at Washington. ... Philadelphia OF Raul Ibanez finished 0 for 3. He is batting .100 (4 for 40) this spring. ... Philadelphia closer Brad Lidge likely won't pitch in a Grapefruit League game, according to Phillies pitching coach Rich Dubee. Lidge, who had offseason elbow and knee surgeries, is on tap to appear in a minor league game Saturday. He is hoping to join the Phillies in mid-April.
