"When you're out there sweating and you're dehydrated to start the game, you're at risk," Werth said. "I knew that going into it, so it's probably more my fault than anything else. But you want to win, you want to help your team win, and the only way I can do that is if I'm on the field."
Werth was 2-for-2 with a pair of singles before his exit on Sunday. He initially felt the pull when fielding a ball in the third inning and thought it was just a cramp. But after collecting his second hit of the day to lead off the fourth, he thought it might be worse.
"When you hit the ball normally, you take a big turn, but he shut it down early," manager Davey Johnson said. "So I knew something was wrong and I was hoping he'd start feeling better, but obviously he wasn't."
Werth came off the disabled list on June 4 after recovering from a strained right hamstring, another injury that he said might have been the result of dehydration. He has missed 31 games so far this season after missing 81 games last year with a broken wrist.
Werth was examined by Dr. Wiemi Douoguih and given fluids during the game.
"I'll know more tomorrow, but I think I'll be all right," Werth said. "Groins are pretty straightforward. I've had a couple of them in the past, but I didn't miss any time, so I hope that'll be the case."
Tom Schad is an associate reporter for MLB.com. Follow him on Twitter @Tom_Schad. This story was not subject to the approval of Major League Baseball or its clubs.