Greg Cook, a Bengals quarterback whose immense talent was never fully realized because of a shoulder injury suffered in his third professional game, has died at the age of 65 after being hospitalized with pneumonia.

The Bengals selected Cook with the fifth overall pick in the 1969 NFL draft and instantly fell in love with his arm, proclaiming him the starter and releasing their starting quarterback from the previous year. Paul Brown, the Hall of Famer who at the time was the Bengals’ head coach and general manager, said, “We believe this young man is the best quarterback prospect in the country.”

Cincinnati started that season 3-0 with Cook leading the way, but in the third win, over eventual Super Bowl champion Kansas City, Cook suffered a serious shoulder injury. He played through the shoulder pain for much of the remainder of that season, but by the end of the year his shoulder was so badly damaged that he would miss the next three seasons, then return to play just one more game before retiring for good.

“I tore my rotator cuff and we didn’t know it at the time because we didn’t have the medical attention that you have today,” Cook recalled years later.

Amazingly, Cook led the league in passer rating, completion percentage, yards per attempt and yards per completion as a rookie playing through a torn rotator cuff. But by the time the season was over and doctors operated, there was little they could do. The relatively primitive surgical procedure used for such injuries in the 1960s required cutting through muscles, which only damaged Cook’s shoulder further.

“Greg was the single most talented player we’ve ever had with the Bengals,” Bengals president Mike Brown said in a statement released by the team today. “His career was tragically short due to the injury. Had he been able to stay healthy, I believe he would have been the player of his era in the NFL.”

In his book Greatest Quarterbacks, Peter King rated Cook as one of the 50 best players ever to play the position, even though Cook played in just 12 professional games. Longtime Sports Illustrated writer Paul Zimmerman called Cook’s rookie year one of the greatest individual seasons any quarterback has ever had, and Bill Walsh, the Bengals’ offensive coach at the time, said years later that Cook could have been the greatest quarterback ever. NFL Network ranked Cook as the greatest one-shot wonder professional football has ever seen.