Dubin was optioned to Triple-A Sugar Land on Sunday.
Dubin logged a 4.17 ERA, 1.57 WHIP, 49 strikeouts, two saves and one win in 45.1 innings for the big club this year. He pitched a clean ninth inning with two strikeouts and a save Saturday, so Dubin may have been optioned simply because he wasn't going to be used Sunday.