Hugh Thornton, an offensive guard who never played a down for the Falcons, retired from the NFL on Thursday.

Thornton, 25, signed March 21 after playing in 37 games and making 32 starts for the Indianapolis Colts after he was drafted in the third round of the 2013 draft.

Thornton, who played at Illinois, had a chance to compete for the Falcons’ vacancy as the starting right guard.

After the draft and signing undrafted rookie free agents, the Falcons now have nine interior offensive linemen on the roster.

Excluding center Alex Mack and left guard Andy Levitre, theoretically the other seven will compete for the opening. With Thornton out of the picture, only Trevor Robinson has started NFL games.

Robinson, who played at Notre Dame, started seven games with Cincinnati (2012) and 14 with San Diego (2014-15) as a center.

Wes Schweitzer and Ben Garland are contenders. The Falcons drafted Sean Harlow in the fourth round and signed former Auburn guard Robert Leff and centers Travis Averill and Cam Keizur.

The backup interior linemen must be functional at center, left guard and right guard.

Chester won a battle over Schweitzer, who was selected in the seventh round of the 2016 draft. Garland played on offense and defense last season.

Mack expects the battle, which will be under the direction of offensive line coach Chris Morgan, to rage well into training camp.

“We have a lot of guys who work really hard,” Mack said. “In OTAs, we’ll get a lot of reps in there. In training camp, we’ll start to narrow it down.”

Schweitzer is considered the early favorite.

“He’s a big powerful guy,” Mack said. “He’s been hitting it pretty hard in the weight room. He’s done a real good job of working hard every day.”