Muller will start Monday's game against the Mariners, Martin Gallegos of MLB.com reports.
Muller served as a long reliever during his last two appearances, but he'll make his first start since July 1 during Monday's series opener against the red-hot Mariners. Over his two outings since rejoining the big-league club, Muller has allowed three runs on seven hits and three walks while striking out six in 7.1 innings.