The Twins recalled reliever Lester Oliveros from Triple-A Rochester after the game because of their depleted bullpen. Oliveros has a combined 2.70 ERA with 38 strikeouts in 36 2/3 innings split between Double-A New Britain and Rochester this season.
Walters gave up four straight hits to Jimmy Rollins, Juan Pierre, Hunter Pence and Jim Thome before he was met at the mound by manager Ron Gardenhire during the 9-8 loss. Gardenhire was then joined by trainer Dave Pruemer, and the decision was made to remove Walters from the game.
Walters told the training staff he had trouble getting loose before the game and that his shoulder was bothering him. But Gardenhire said they had no indication Walters had problems with his shoulder until they saw his fastball in the low 80s to start the game.
"When I went out there he said he was fine, but I told him, 'You're not fine. You're throwing 80 mph,'" Gardenhire said. "He was trying to save our bullpen. Finally he told me he had a sore shoulder. But no one knew about it. He never said anything."
Right-hander Jeff Manship came in and allowed both inherited runners to score, as he served up a three-run homer to John Mayberry later in the inning.
Walters was credited with allowing four runs on four hits without recording an out. He threw 15 pitches, 10 for strikes.
"I was stiff and just couldn't get it going," Walters said. "Guys pitch through that all the time, but today it just wasn't going to loosen up. I've never missed a start before. Obviously, I don't think I'll be throwing in five days, but hopefully it's no big deal."
With an off-day on Monday, the Twins don't need a fifth starter until June 23. Right-hander Liam Hendriks remains the favorite to be recalled from Rochester in time to start against the Brewers on Saturday.