Gagne will be examined by a team doctor in Philadelphia.
The Team Canada doctor doesn't believe the injury is serious but Gagne is returning for a second opinion anyway, said Flyers General Manager Paul Holmgren.
Gagne was hurt Monday evening and will have his follow-up exam with Flyers doctor Peter DeLuca on Wednesday, according to Holmgren.
The left wing is a vital offensive weapon for the Flyers. He was third on the team with 74 points last season and scored 34 goals, good for second on the team behind Jeff Carter.
Gagne, who had hip surgery to remove a bone spur and adhesions in May, said he felt tightness in his hip and groin as Monday night's practice started.
"I thought it was going to be an easy practice, but the tempo was very fast right away during the very first drill. Guys were obviously trying to show their best. I had been skating back home for about two weeks but not at that high level. I kind of felt that it was getting a little bit tight on me, close to the hip and groin," he said.
Gagne talked to the trainers and "they pulled me out and there was really no question to try to push it again," he said.
In returning to skating after the surgery, Gagne said he has felt tightness before that turned out to be no cause for concern and he is just being cautious by having the Flyers doctor examine him again.