Polanco chased after Josh Donaldson's fly ball to shallow right field but couldn't get to it in time, and the ball landed for a single. Polanco came up limping, favoring his left leg, and exited the game with head athletic trainer Todd Tomczyk.
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Polanco has already been sidelined twice this season by a strained left hamstring, most recently sitting out from July 22 until Aug. 2. The specific nature of his latest injury was unclear when he left the game.
McCutchen exited Friday's game with left patellofemoral discomfort, a knee injury that he did not believe to be serious. McCutchen hit in an indoor cage before Saturday's game but did not start.
Super-utility man Sean Rodriguez replaced Polanco in Pittsburgh's lineup and played left field. John Jaso moved from left to right field.
Injuries have limited Polanco to 90 games this season. His production at the plate and on the bases has also dipped after an improvement last season. Polanco is slashing .255/.311/.407 with 10 home runs, 32 RBIs and eight steals this year.
Adam Berry has covered the Pirates for MLB.com since 2015. Follow him on Twitter and Facebook and read his blog. This story was not subject to the approval of Major League Baseball or its clubs.