FOXBOROUGH, Mass. — For months the biggest question facing the Patriots was whether Tom Brady would be on the field for the start of the 2016 regular season.

While that question has been answered, it’s not the only issue to resolve for New England’s offense as it prepares for its third preseason game.

Running back Dion Lewis has yet to appear in a training camp practice or preseason game. He had ACL surgery on his left knee in November and now reportedly could be facing a second procedure.

There are also health concerns on the offensive line. Sebastian Vollmer was expected to be the starter at right tackle, but has missed both preseason games and remains on the physically unable to perform list with an undisclosed issue.

In addition, guard Shaq Mason, who was not in uniform last week against Chicago after starting the preseason opener, reportedly has a broken hand. Lewis, Vollmer and Mason were all absent from the practice field on Monday.

Brady was also absent after not being on the sideline for his second straight preseason game. Coach Bill Belichick declined to give details, saying only “I don’t comment on any personal situations.”

What Belichick has acknowledged is that because of Brady’s upcoming four-game “Deflategate” suspension, the priority is to get Jimmy Garoppolo ready to play.

The Patriots were hoping to see Lewis, who had four touchdowns in seven games before his injury last year, ready in time for the regular season after getting him back on the field in June during their offseason program.

Losing Mason would also be a setback after he appeared in 14 games with 10 starts in 2015. The same can be said for Vollmer, a fixture on New England’s line since arriving in 2009.

The most likely candidate to step into Vollmer’s spot at right tackle is Marcus Cannon.

BRONCOS: Coach Gary Kubiak named Trevor Siemian the starter for the Broncos’ third preseason game over Mark Sanchez and said he will decide next week who will be under center against Carolina for the season opener on Sept. 8.

49ers: Colin Kaepernick is on track to make his preseason debut Friday against the Packers in San Francisco’s third preseason game.

WASHINGTON: Matt Jones will miss the rest of the preseason with a left shoulder injury, but Washington hopes its top running back will be ready for the start of the regular season.

GIANTS: New York signed place-kicker Randy Bullock and waived free agent Tom Obarski.

The Giants made the move Monday, electing to sign a veteran with Josh Brown suspended for the regular-season opener against Dallas on Sept. 11.