Giles was optioned to Triple-A Fresno on Wednesday.
Giles was roughed up for three runs on three hits Tuesday against Oakland as he failed to retire a single batter out of the bullpen. He'll look for more success with the Grizzlies after pitching his way out of the closer role, posting a 4.99 ERA and 1.27 WHIP with 31 strikeouts across 30.2 innings with the big club.