Tomas was optioned to Triple-A Reno on Thursday.
Tomas spent less than a week with the big club, going 0-for-6 with a trio of strikeouts in four appearances (one start) during that stretch. He'll return to Reno, where he owns a .305/.341/.603 slash line and 29 home runs in 98 games this season. This move frees up a spot on the active roster for Mike Leake, who was acquired from the Mariners on Wednesday in exchange for Jose Caballero.