Topa was recalled from Triple-A Nashville to serve as the 29th man for Thursday's doubleheader against the Giants.
Topa was sent down in mid-August after being reinstated from the 60-day injured list, but he'll join the big-league club for its doubleheader against San Francisco. The right-hander has posted a 3.71 ERA and 1.65 WHIP in 17 innings over 15 relief appearances at Nashville this year and should serve as an extra arm in Milwaukee's bullpen Thursday.