HOUSTON — Atlanta quarterback Matt Ryan has thrown just one pass this season without Alex Mack snapping him the football. But after an alarming session at Thursday’s practice at Rice University — just three days prior to Super Bowl LI — it appears there’s a chance the Falcons are in danger of Mack not playing every snap on Sunday in the biggest game of his career.

Mack struggled with his injured left fibula in Atlanta’s final full-speed practice before the Super Bowl, according to PFWA pool reporter Peter King.

“I just know his toughness and strength is so great,” Quinn said after another brisk and quick (88 minutes) practice Thursday. “The good thing is I know he’s feeling better than he did in the NFC Championship Game. But yeah, I’m concerned. I’m not panicked, but I’m concerned.”

Mack did practice on Thursday, but also was seen working on the side with backup center Ben Garland. From King’s pool report:

Mack was seen coaching backup Ben Garland off to the side on technique work. That’s a mark of how the Falcons practice; often, receivers are seen coaching receivers, or quarterback Matt Ryan discusses technique or positioning with receivers and backs, or linemen coach linemen. Garland, a studious type, has been working overtime on New England tape with Mack in the past week.

“This game, because of the multiple fronts by New England, requires a lot of prep work by the center,” Quinn said. “Identifying this look, this front, this player’s positioning, they [Mack and Garland] spend a lot of time in the film room together normally … and I would say it’s been even more these two weeks because this opponent requires even more.”

The addition of Mack as a free-agent signing prior to the 2016 season has been widely lauded as the best move of the Falcons’ offseason, and Mack has been given a ton of credit for stabilizing and helping the offensive line improve. If unable to play the entire game, his loss would be felt, greatly.