Once their biggest priority of the offseason, Jon Beason has become the Giants’ biggest concern of the offseason. And it’s a concern that could spill into the regular season.

The starting middle linebacker whom the team re-signed to a four-year deal worth up to $19 million will be sidelined for the next several months after suffering a ligament tear and a small fracture to the sesamoid in his right foot during Thursday’s OTA.

According to the Giants, Beason underwent X-Rays, an MRI and CT scan at the Hospital for Special Surgery where he was examined by team physician Dr. Russell Warren and HSS foot and ankle specialist Dr. Martin O’Malley.

On Monday, Beason will undergo further examination and review of his injury with foot and ankle specialist Dr. Robert Anderson in Charlotte, N.C. A determination will then be made regarding the next steps in the repair and rehabilitation from the injury.

Whether or not surgery is required, the injury is expected to take 12 weeks for recovery. The Giants open the regular season on Sept. 8, exactly 12 weeks from Monday.

“The prognosis is X amount of time and [the opener] is within that timeframe,” Beason said. “I expect to be back [for that game]. If not, I’ll be back as soon as I can. That’s really how you have to look at it. If it’s not 16 [games played], maybe it’s 15 or 14. Whatever it is, you want it to be that number as opposed to one.”

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The Giants had two players race back from surgery to play in the opener last year with both Jason Pierre-Paul and Henry Hynoski meeting that deadline. Neither was ever fully recovered, though, and both had disappointing seasons that ended with them inactive due to other injuries. The Giants would rather be patient with Beason than lose him for an extended period of time during the regular season.

Anderson is the team orthopedist of the Panthers, the team Beason played for from 2007 until his trade to the Giants last fall. Anderson operated on Beason’s torn Achilles tendon in 2011. He also was the surgeon who performed the arthroscopic procedure on Eli Manning’s ankle this spring.

Beason has fought through knee and Achilles surgeries in his career and returned to become a force for the Giants in just 11 games in 2013. He was expected to be named a defensive captain this fall, replacing Justin Tuck in that role.

“I know that mentally you can’t get down on yourself,” Beason said. “You have to understand the situation and what you can control. The toughest part is knowing that there are a lot of people obviously in the locker room, the coaching staff, the organization and even the city that are counting on me to do my part and do it well.”

The Giants are expected to move veteran outside linebacker Jameel McClain to the inside to replace Beason until his return. They also have Mark Herzlich and rookie Devon Kennard on the roster. Kennard stepped in for Beason when he was injured on Thursday, but knowing the extent of the injury it’s unlikely he’ll remain there.

Coughlin stressed on Thursday that Beason’s role on the team and the defense is “very important because of the nature of the player, the man, his attitude, what he brings to the table, his leadership skills.”

There was some concern that Beason’s 2014 season could have been over when he limped off the field in the next-to-last OTA of the spring and had to be carted out of the fieldhouse on Thursday.

“It’s just one of those things, you have freak injuries,” Beason said. “I literally felt like I stepped in like a sprinkler head hole. I just felt it give right away, so the next step I knew I couldn’t put the foot down. I had a bad feeling. I really felt that I had torn the extensor, which is the tendon with the muscle, it’s how your big toe functions. That would have been season-ending. So at least now there’s a procedure, possibly … It’s not season-ending, so I’m happy about that.”