San Diego manager Bud Black said Gerut, who suffered the injury to his finger during Wednesday's 5-4 victory over the Diamondbacks on a stolen-base attempt, is "feeling a lot of discomfort."
"Hopefully, each day it gets a little better. We'll see how he is tomorrow. But I'm not hopeful," Black said.
Black said there's a chance Gerut could play Monday when the Padres open a three-game series against Los Angeles at Dodger Stadium.
Gerut is hitting .297 this season with 14 home runs and 43 RBIs. Gerut is hitting .322 in August with seven home runs and 19 RBIs.
Rookie Will Venable started in center field for the second straight day. On Friday, Venable got his first Major League hit in his first at-bat, a triple.
The Padres are short-handed when it comes to outfielders, as Scott Hairston was lost for the season when he was placed on the disabled list Friday with a torn ligament in his left thumb.
Corey Brock is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.