Report: Richardson facing month-plus absence due to Grade 3 AC joint sprain

Indianapolis Colts quarterback Anthony Richardson is set to miss at least a month after receiving an initial diagnosis of a Grade 3 joint sprain, sources told Ian Rapoport of NFL Network.

Richardson will undergo an MRI on Monday morning to confirm the severity of the right shoulder injury, Rapoport adds. He will also seek a second opinion from renowned shoulder specialist Dr. Keith Meister, sources told Jeremy Fowler of ESPN.

Colts head coach Shane Steichen said Monday that Richardson will miss "some time" with the injury, but the team is still evaluating whether he'll go on injured reserve, which requires a minimum four-game absence, according to Cameron Wolfe of NFL Network.

Steichen confirmed Richardson will miss the Week 6 matchup with the Jacksonville Jaguars and Gardner Minshew II will start.

It's the second significant injury of Richardson's rookie season: He missed Week 3 with a concussion. He also tweaked his ankle at the end of his NFL debut, though Steichen said he could've returned if needed.

The 21-year-old suffered the shoulder injury while being tackled on a designed quarterback run during Sunday's win over the Tennessee Titans. He immediately pointed to his throwing shoulder before going to the locker room.

Richardson, the No. 4 overall pick, has shown off his dynamic playmaking abilities to start his NFL career. He's racked up 577 passing yards and three touchdowns against one interception while also adding 136 yards and four scores on the ground.

Minshew led the Colts to victory over the Titans to improve their record to 3-2. The veteran signal-caller has performed well in relief of Richardson, completing 68.7% of his passes for 553 yards and two touchdowns.

The 27-year-old Minshew, who split the first four years of his career between Jacksonville and Philadelphia Eagles, has 25 career starts and 12 further appearances.

Indianapolis is scheduled to play the Jaguars, Cleveland Browns, New Orleans Saints, and Carolina Panthers over the next month.