The Seattle Mariners put right-hander Felix Hernandez on the 10-day disabled list with a sore back.
Hernandez, 32, is 8-7 with a 5.13 ERA in 19 starts with the Mariners this season.
The six-time All-Star and one-time ace of the staff has the highest ERA in the starting rotation for the Mariners, who are 57-34 -- three games back of the Houston Astros in the AL West and second in the wild-card standings.
In other roster moves, the Mariners recalled infielder Gordon Beckham and right-hander Nick Rumbelow from Triple-A Tacoma, and outfielder John Andreoli was optioned to Tacoma.