As Anthony Richardson deals with his third injury four games into his NFL career, concern is already starting to mount regarding his long-term health.

Richardson left Sunday's game against the Tennessee Titans with an AC joint sprain in his right shoulder, per Ian Rapoport of NFL Network, leading to one rival coach to compare his body type unfavorably to Cam Newton.

"Cam [Newton] was 250-260 pounds and thick," the coach told Mike Sando of The Athletic. "Richardson has a much leaner look to him. Cam delivered punishment. Richardson takes punishment. Big difference."

Richardson has suffered three different injuries in his NFL career already. He went down with a minor knee injury in Week 1, suffered a concussion in Week 2 that forced him to miss Week 3's win over the Baltimore Ravens and now is dealing with an injury to his throwing shoulder.

Depending on the severity of the ACL joint sprain, Richardson could be out for several weeks. Jeremy Fowler of ESPN reported the Florida product is seeking a second opinion on his shoulder, as he and the team are "still charting course and gathering info."

It's likely the Colts will lean on the conservative side regardless of Richardson's diagnosis. He's already a rookie who came into the NFL with just 13 college starts on his resume; his inexperience was always going to lead to taking hits. Combine that with his aggressive running style, and it was only a matter of time before Richardson found himself dealing with some sort of injury.

That said, the frequency of Richardson's injuries so early in his NFL career is a concern. If we're comparing Richardson to Newton, the latter did not miss a game in his first three seasons and missed no more than two in a season over his first eight years in the league.

Newton's battering-ram style also led to him dealing with a number of nagging injuries and being out of the NFL by age 32. The Colts will have to find a way to better protect Richardson if they won't want that history repeating.