Nick Fairley said he has gained seven pounds since the start of training camp and, after nearly two weeks in a backup role, the big defensive tackle is hopeful that he’ll regain his starting job with the Detroit Lions by preseason’s end.

“Really, what I plan on doing is just continue to get better as a player and help this team and just go out there and play my (tail) off,” Fairley said today, in his first public comments since his demotion.

The Lions elevated C.J. Mosley to Fairley’s starting spot for last week’s game against the Oakland Raiders, and Fairley, the 13th overall pick in the 2011 NFL draft, has continued to work with the second-team defense in practice this week.

Fairley spoke with reporters for five minutes in front of his locker today and presented a brave and upbeat face.

He said his weight, as low as 295 pounds after sleep apnea surgery this off-season, ballooned in recent weeks because “my eating habits got out of the way.” But he said he’s comfortable at his current playing weight of 315 pounds.

Last year, Fairley played as heavy as 322 pounds. He reported to camp last month at 308.

“With big guys, for the most part, you always have an issue with trying to get a weight that they’re comfortable with and getting into a routine,” defensive coordinator Teryl Austin said. “And sometimes when you change routines, whatever your summer routine is to come here, you’ll have some ups and downs. And I think that’s where Nick was, and he’s starting to figure out where he needs to be and he’s working towards that goal.”