Polanco dislocated his throwing shoulder on an awkward slide into second base on a double last Friday against Miami. He had surgery Wednesday to repair the labrum and stabilize his shoulder, and the Pirates said Friday the typical recovery time for that type of surgery is seven to nine months.
That would put Polanco on track to return between mid-April to mid-June.
Polanco, who turned 27 on Friday, leads the Pirates with a career-high 23 home runs, 81 RBIs and 61 extra-base hits. He batted .254 this season.
"He'll have the support of his family, he'll have the support of the organization, he'll have the support of a lot of people," Pirates manager Clint Hurdle said before the game in Milwaukee.
"He's a man that's always been self-motivated, focused. Now is the healing, the rehab, and the strengthening and then the getting ready to play, whenever that is. We'll look forward to that," he said.
With Polanco out of the lineup, four players will be vying for time in right field, Hurdle said.
"It's going to be a daily decision on who we want to play second base and do we want to move Kramer to third base," Hurdle said. "We did that the other day."
Luplow got the start in right on Friday night against the Brewers and went 1-for-3 with an RBI triple in the third. Milwaukee won 7-4.
The Pirates also said pitcher Chad Kuhl, on the disabled list since June with forearm and elbow tightness, is scheduled to be re-examined after he was unable to throw his scheduled side session earlier this week.
The Associated Press contributed to this report.