Tsao took the loss on Saturday night against the Padres, walking the final three hitters he faced to force in the winning run in the 11th inning at Petco Park. He was the only Dodgers reliever not used in Sunday's 17-inning marathon, instead sitting in the Dodgers dugout the entire game.
"He pitched on Saturday, then on Sunday morning he came in and said he had a sore triceps," manager Dave Roberts said. "Because we learned of this late, we couldn't make a move yesterday."
The DL move was made retroactive to Sunday.
Placing Tsao on the disabled list was the needed move to be able to bring back Mike Bolsinger within 10 days of getting optioned. Bolsinger started for the Dodgers last Wednesday, was optioned back to Triple-A Oklahoma City on Thursday, and under normal circumstances would have been ineligible to return Sunday, May 29.
Tsao, 35, pitched in two games for the Dodgers this season, allowing a run in 1⅓ innings, with three walks and no strikeouts. He had a 3.86 ERA and six saves in 17 games with Oklahoma City this season, with 14 strikeouts and five walks in 16⅓ innings.