TORONTO (AP) The Houston Astros have activated right-hander Luke Gregerson off the disabled list and selected outfielder Teoscar Hernandez from Triple-A Fresno.

The Astros said outfielder Colby Rasmus underwent surgery Wednesday to remove a cyst from his ear.

Rasmus went on the disabled list Sunday after being bothered by the ear for some time. He is expected to return in September.

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Hernandez is making his major league debut in center field against the Blue Jays and left-hander Francisco Liriano on Friday night.

Houston put outfielder Preston Tucker on the 15-day disabled list because of a strained right shoulder and placed right-hander Ken Giles on the paternity list.

Gregerson is 3-1 with 14 saves and a 3.09 ERA. He has been out since July 27 with a strained left oblique.

Hernandez hit .307 with 10 home runs and 53 RBIs in 107 games between Double-A and Triple-A this season.