Former NFL tight end John Carlson retired from pro football earlier this offseason, just before his 31st birthday. Carlson, a second-round draft pick in 2008, was productive as recently as last season, so his sudden retirement is somewhat surprising.

However, after seven seasons with the Seattle Seahawks, Minnesota Vikings and Arizona Cardinals, Carlson simply lost the feelings he once had for the game.

"It was clear already that I didn't have that same passion and love for the game that I had in the past," Carlson told Chip Scoggins of the Star-Tribune.

Early retirements are a growing trend in the NFL, and Carlson shares a connection with the players who have left the game due to concern about head injuries. The former tight end has endured at least three concussions during his playing career, according to the Star-Tribune.

"I think once that switch turns off in your head," Carlson said, via the Star-Tribune, "I don't believe the game is safe to play anymore."

Carlson finished his seven-year career with 210 receptions for 2,256 yards and 15 touchdowns. His most productive seasons came early in his career with the Seahawks.

(h/t Star-Tribune)

Photo Credit: Brace Hemmelgarn/Contract Photographer