EAGAN, Minn. — Vikings Head Coach Mike Zimmer said Monday that Dalvin Cook is considered "day-to-day" with a shoulder injury.

"We'll just see how Dalvin is doing," Zimmer said. "It will be day-to-day and see where it goes."

Zimmer declined to reveal the specific nature of Cook's injury and said he was unsure if the running back would play Sunday against the Lions.

"I don't know," Zimmer said. "It's day-to-day … that's what they're telling me."

Cook, who underwent an MRI on Monday, injured his shoulder late in the third quarter Sunday at San Francisco and left the game after a scary play.

The running back was tackled for a loss of 4 yards and fumbled, but he was shaken up after the play and had to leave the game on a cart.

Cook, who was quickly ruled out with a shoulder injury, was attended to by trainers and encouraged by players on both teams as he left the field.

Vikings wide receiver Adam Thielen on Monday said the offense will have to find a way to be productive without Cook, who ranks fifth in the league (and leads the NFC) with 773 rushing yards.

"If he does miss a game, obviously he'll be extremely missed," Thielen said. "His play on the field, his leadership ability, things like that.

"But at the end of the day, we'll figure that out this week," Thielen added. "And then we'll put our best foot forward as far as trying to move the ball and score points and help this team win."

Cook's injury could open the door for Alexander Mattison, who has made two starts in Cook's place already this season.

Mattison shined with 112 rushing yards against Seattle in Week 3, and then set a new career-high with 113 rushing yards against Detroit in Week 5.

The 2019 third-round pick has made four career starts, tallying 95-plus rushing yards in three of them.

"He's done a nice job when he's been in there," Zimmer said. "We anticipate him, if he has to play, going in there and playing well."