In his first appearance in the major leagues since breaking a bone in his left ankle last July 6, Frank Thomas strained a hip flexor and left in the seventh inning Monday as the Chicago White Sox beat the Los Angeles Angels 5-4. Thomas, who went 0-for-2 with a walk, said his latest injury wasn't serious. "I just felt a little twinge in the hip flexor," he said. "It was just one of those things you don't want to get out of hand by hitting a line drive and having to leg it out. It's a day-by-day situation, and I'm feeling good. I didn't want to go out on the first day and be down for two weeks."