SAN FRANCISCO -- Joc Pederson had been enjoying his trip back to Oracle Park, where Giants fans know him well from his days with the rival Dodgers. Multiple times, the Cubs outfielder could be seen egging on the fans heckling him from the left-field bleachers.

"They were going to boo me or do whatever anyways," Pederson quipped on Friday. "I think the best thing you can do is embrace it."

Things took a more sour turn for Pederson on Saturday, when he exited the Cubs' 4-3 loss to the Giants in the fifth due to tightness on the right side of his lower back. The issue comes as Chicago is already working with a depleted outfield corps.

Cubs manager David Ross said Pederson tweaked his back when the outfielder hit the left-field wall awkwardly in the third inning. Alex Dickerson launched an 0-1 sinker from Cubs righty Kohl Stewart to left, where Pederson turned at the last second before hitting the padding, as the ball dropped just over the fence.

“He was kind of dealing with it when he ran into that wall,” Ross said. “It just messed up his back a little bit. He seemed to loosen it up. I think he was probably about 70 percent."