The knee hasn't kept him from taking swings in the batting cage, and his next step before returning is being able to move around at full speed.
"He's had difficulty running at the speed he needs to for a Major League game," said Padres manager Bud Black.
Quentin has been receiving treatment on his knee and has been working in the weight room while he waits to return. He is hitting .275 with 13 homers and 45 RBIs in 82 games this season.
His knees have given him trouble all season long after having surgery on his right knee at the end of the 2012 regular season, so the Padres have handled him with care, giving him off-days whenever possible.
Black dismissed any notion that Quentin should decrease his intensity in the outfield to help cut down on the wear and tear on his knees, especially since this latest injury came on an awkward swing.
Mark Kotsay started for Quentin in left field on Sunday.
Jamal Collier is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.