Pittsburgh recalled catcher Elias Diaz from Triple-A Indianapolis, giving the Pirates protection with starting catcher Francisco Cervelli battling a left wrist injury.
Polanco missed eight and nine games with his previous two left hamstring strains.
"We don't have a timetable," Pirates manager Clint Hurdle said. "I'd imagine it could have some distance other than the 10 days, based on the injury being the third time it has happened in the same spot."
Instead of recalling an outfielder, Pittsburgh opted to bring up Diaz for the time being in order to give Cervelli the two-game series against the Brewers off. Chris Stewart will start behind the plate both games in Milwaukee with Diaz serving as the backup.
Hurdle said Cervelli's wrist injury is not to the point where a trip to the disabled list is necessary. Playing through the injury also wasn't an option, leaving the Pirates to try giving Cervelli three consecutive days off, which included Monday's off-day.
"We'll use him if we need to use him, but we'd like to stay away from him," Hurdle said. "We felt that a DL option at this time was outside the window of what would make sense. This is an injury he will need to play through. However, this is an opportunity for us to calm it down a little bit."
Polanco is batting .255 with 10 home runs and 32 RBIs in 91 games for the Pirates this season. The 25-year-old suffered the injury chasing down a liner off the bat of Blue Jays third baseman Josh Donaldson in Saturday's game. He left the contest early and did not play Sunday.
Diaz joins the big league club for the third time in 2017. The 26-year-old enters Tuesday's game with a .266 average and a homer to go with 14 RBIs in 30 games across two separate stints with Pittsburgh earlier this year.
If Cervelli is able to return at some point during Pittsburgh's four-game weekend series with St. Louis, the Pirates could option out Diaz to call up an outfielder. For the time being, Hurdle said Adam Frazier will see time in right field with John Jaso and Jose Osuna as other outfield options.
"I anticipate the way [Frazier] has been swinging the bat that he is going to get some shots," Hurdle said.
McCutchen back in the field
Pirates outfielder Andrew McCutchen returned to center field Tuesday after not playing the field the past two games due to left patellofemoral discomfort. McCutchen left Friday's game in Toronto early and sat out Saturday before serving as the designated hitter on Sunday.
Andrew Gruman is a contributor to MLB.com based in Milwaukee who covered the Pirates on Tuesday.