The squirrel appeared to enter the field from along the stands on the third base side of the stadium before running into the left field corner as it evaded being caught by three grounds crew members.
Initially, Pirates play-by-play man Greg Brown was confused as to why the home crowd began cheering for a 2-1 pitch early in a scoreless game before spotting the critter.
“Ahh, the crowd is cheering the squirrel,” Brown said.
“Now where’s this squirrel live?” analyst Bob Walk asked, confused by the situation. “There’s no trees out here.”
The squirrel then ran off the field and through the open bullpen gate.
"Well we can play now, he's in the bullpen," Walk added after the grounds crew closed the door on the squirrel.
Apparently, the squirrel served as a good luck charm for the Pirates, who went on to score three runs in the second inning en route to a 12-1 victory against the Cubs, extending their winning streak to three games.
The victory extended the Pirates' third-place margin over the Cubs to 2.5 games in the National League Central standings, through Pittsburgh still remains 10.5 games behind the first-place Milwaukee Brewers, who defeated the second-place St. Louis Cardinals, 2-0, on Monday.