Denver Broncos quarterback Drew Lock will undergo an MRI exam on his right passing shoulder after sustaining a game-ending injury early in Sunday’s contest against the Pittsburgh Steelers.

According to ESPN, Lock suffered a sprained AC joint and is expected to miss at least two weeks and as many as six.

The 23-year-old Lock was injured on Denver’s second drive midway through the first quarter after he was sacked by Steelers linebacker Bud Dupree. Lock stumbled before fumbling the ball, which was recovered by Pittsburgh.

Lock went to the blue tent on the sideline before retreating to the locker room. He completed 1 of 5 passes for 20 yards before being replaced by Jeff Driskel.

During his postgame interview, Lock wore a black sling.

“We’re going to take it day by day,” Lock said. “I’m optimistic about it. We’ll have it checked out (Monday) morning, and we’ll know more then.”

Lock said he tried a couple passes on the Broncos sideline after the injury and knew something was not right.

“It felt funny,” he said. “I’m not going to blow it out of proportion on how funny it felt. It’s just, I’ve been throwing the football my whole life, and I wouldn’t say it necessarily felt normal.”