Nationals right-hander Craig Stammen, who was placed on the disabled list Wednesday, will require surgery to repair a flexor tear in his right arm.
The team tweeted the news Thursday, a day after Stammen was shelved and right-hander Taylor Jordan was called up from Triple-A Syracuse. On Thursday, lefty Felipe Rivero was called up to take Jordan's place on the roster.
Stammen, who has appeared in 49 or more games in each of the last three seasons for Washington, had been experiencing pain in his forearm since Sunday. The pain subsided a bit early in the week, and he pitched a third an inning against the Red Sox on Tuesday but again felt pain.