Ridley sustained the injury during the third quarter of the Patriots' win over the Buffalo Bills on Sunday. He had a brace over his knee and walked with a cane when leaving Ralph Wilson Stadium. He had an MRI on Monday.
The injury occurred on a play where Ridley was upended by a Bills defender.
Ridley has 340 rushing yards and two touchdowns on 94 carries in six games this season for the Patriots. In his career, the 25-year-old has 22 career rushing touchdowns and has missed only two games, both last season.
Mayo had 53 combined tackles, a fumble recovery and one sack this season.
The Patriots (4-2) will host the Jets (1-5) Thursday night.
- Molly Geary