After he was examined by team medical director Dr. David Lintner later that evening, the club confirmed the right-hander would indeed remain in the rotation.
Oswalt left his most recent start on Saturday against the Rangers in the seventh inning with what was originally announced as a right groin strain, but the right-hander says the pain is in his inner right hip. He intends to test the area again Tuesday with another long-toss session but doubts he'll have to skip a start in order to heal.
"It's not a muscle strain, so that's a good thing," he said. "I think it's more of a tendon ... I think it's just inflamed more than anything."
Oswalt speculated this could be a result of being hit twice in that area with batted balls this season. He's also relieved it's not a groin problem, which hampered him several times during the 2003 season and eventually required surgery.
"I knew this wasn't muscular," he said. "The years I had the groin [strain], once I felt it, I was done. This, I could actually pitch through it. Just an achy feeling more than anything."
Alyson Footer is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.