INDIANAPOLIS – Colts rookie quarterback Anthony Richardson could miss at least a month after being injured in Sunday’s game.

That’s according to the NFL Network’s Ian Rapoport, who reported, citing sources, that Richardson was diagnosed with a Grade 3 AC joint sprain of his right shoulder.

Rapoport said the injury would keep Richardson out for “a month or more,” adding that the Colts QB would have another MRI Monday to confirm its severity.

The rookie was hurt on a 4-yard run with 4:29 remaining in the first half. He fell to the turf awkwardly while being tackled by a pair of Tennessee Titans defenders. Richardson stayed down and immediately pointed to his right shoulder.

He then walked to the blue medical tent before heading to the locker room for further examination. His right arm dangled as he went to the locker room; he leaned to his right and clearly favored the injured shoulder as he walked.

It happened on a designed running play. Head coach Shane Steichen said during this postgame news conference that Richardson’s size and speed make him unique.

“When you have a dynamic player like him, obviously one of his skillsets is as a runner,” Steichen said. “That’s what makes him really good. The designed run that he got hurt on, we ran something similar to that last week where he popped it for a big one, then obviously this week he got the shoulder on that play. That’s stuff that you gotta look at and be smart with and it’s part of the game. You don’t want it to happen for sure.”

This marked the third time in four games that the rookie left with an injury. He suffered a bruised knee late against Jacksonville in Week 1 and left in the first half of the Colts’ Week 2 win over Houston after suffering a concussion. He sat out Week 3 against the Ravens and returned against Los Angeles, playing the whole game in Week 4.

Backup Gardner Minshew replaced Richardson during the Titans game. Minshew finished 11 of 14 for 155 yards, directing the Colts to three scores (one TD, two field goals) in relief as the Colts beat Tennessee 23-16.

It’s highly likely Colts fans will see Minshew under center in the weeks to come.