Torrealba will be in uniform wearing No. 3 for the Brewers on Saturday, their second of four games against the Nationals this weekend at Nationals Park.
The 34-year-old catcher played just 10 games for Toronto, batting .214 (6-for-28) with one homer. He spent the start of the season with the Rangers, for whom he hit .236 with three homers in 49 contests.
"It makes us more flexible with what we can do," Brewers coach Ron Roenicke said. "If I want to pinch-hit one of our other catchers early, I feel good doing it. If I want to pinch-run for one of them, we can do it. So it definitely gives us more flexibility."
Torrealba joins Jonathan Lucroy and Martin Maldonado as the third catcher on the Brewers' active roster. The veteran backstop has played in the postseason with the Giants (2003), Rockies ('07 and '09) and Rangers ('11) during a 12-year career spent with six teams. He would not be eligible for postseason play should the Brewers qualify, however.
Milwaukee entered Friday's action 2 1/2 games behind the Cardinals for the second Wild Card spot in the National League.
"We think that it can make a difference; not that it will, but it can make a difference," Roenicke said. "Sometimes you think something is needed, but then you end up and you don't need it at all. So we'll see.
"We've put ourselves in a position where if we play great ball through the rest of the season, we've got a legitimate shot."