Sabathia, who already is on the disabled list with fluid in the knee, will receive a cortisone and stem cell shot in hopes of aiding the issue.
Cashman said the team was "not sure yet" what this will do to Sabathia's timetable.
"There are degenerative changes in the knee," Cashman told a small group of reporters prior to Wednesday's Yankees-Mets game.
On Tuesday night, Yankees manager Joe Girardi said Andrews confirmed there was no structural damage but did not mention the degenerative change.
"I know he saw Dr. Andrews," Girardi said. "I think he agreed with the MRI. It's basically rest, get it to calm down and see when we can get it out there."
Sabathia had surgery to repair a torn meniscus in that knee in October 2010, and the left-hander feared it could be the same issue again.
He underwent an MRI on Sunday morning, had the knee drained of fluid Monday and was placed on the 15-day disabled list.
The Yankees hope the two weeks off will calm the issue. In eight starts, Sabathia is 3-4 with a 5.28 ERA.
ESPNNewYork.com's Kieran Darcy contributed to this report.