Four-time Pro Bowl linebacker Patrick Willis underwent an MRI exam Monday on his injured right hamstring.
The results revealed a Grade-two hamstring strain for the Niners’ star defender.
The Ole Miss product landed awkwardly after missing a tackle on fullback Brit Miller during an 18- yard completion from A.J. Feeley with 4:28 left in the first quarter of Sunday’s 26-0 shutout of St. Louis.
Willis was briefly down before being helped off the field by trainers. He watched the rest of the game in a sweat suit.
To find out how long Willis could be sidelined, go to 49ers Gab