Minnesota Vikings running back Adrian Peterson, who exited Sunday night’s win over the Green Bay Packers with a knee injury, has been diagnosed with a torn miniscus, head coach Mike Zimmer told KFAN Sports Radio in Minnesota.

The timetable for Peterson’s injury is unknown, with ESPN’s Adam Schefter reporting Zimmer not yet ruling out the possibility Peterson could play this week.

The 31-year-old back has struggled through two games this season, picking up just 50 yards on 31 attempts. His longest rush of the season has been nine yards, while his 1.6 yard average is well below his 4.9 yard career average per rush.

Matt Asiata and Jerick McKinnon, who filled in when Peterson was suspended in 2014, figure to once again share the backfield while Peterson is injured.

The Vikings lost starting quarterback Teddy Bridgewater to a torn ACL prior to the season, but have started 2-0 under Shaun Hill and Sam Bradford.