Thompson wasn't especially effective at the start of the season, allowing five runs on 10 hits in 6 2/3 innings. That garnered him a stint at Memphis, where he made three starts with a 3.45 ERA, nine strikeouts and only one walk in 15 2/3 innings.
"We sent him down to get sharp," said manager Tony La Russa, "and he came back sharp."
Thompson takes the exact role that Walters had held, serving as a multi-inning option in case of a short stint by a starting pitcher or extra innings. Walters was better than his numbers might indicate in his first stretch in the Majors, but it's hard to overlook a 9.58 ERA in 10 1/3 innings. Walters recorded 10 strikeouts, but also six walks and three homers.
For Thompson, it's a welcome return. He also hopes it's an end to the shuttling between St. Louis and Memphis that has marked much of his career.
"Today was going to be my start day in Omaha," he said. "Kind of glad I missed that."
Matthew Leach is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.