DAVIE, Fla. -- Lamar Miller seems to have tightened his grip on the starting running back job.
Fellow running backs Jay Ajayi, a fifth-round pick from Boise State; Damien Williams; LaMichael James and Mike Gillislee haven't taken nearly as many snaps with the first team. But Miller, who rushed for 1,099 yards last season and averaged 5.1 yards per carry, is experimenting with more bulk to see if he can carry the load.
The Dolphins signed Knowshon Moreno last year and drafted Ajayi this year in search of someone who can run with a more physical style than the speedy Miller. Noticeably bigger in his chest and arms, Miller is up to 221 pounds, five pounds heavier than his playing weight from last season.
"I'm just trying to find a weight where I'm comfortable right now," Miller said. "I'm undersized. I'm just trying to find something I'm comfortable with."
--Miami signed defensive tackle C.J. Mosley to a one-year contract, providing some run defense reinforcements and reuniting the 11th-year player with fellow tackle Ndamukong Suh. The pair played together the last two seasons in Detroit.
Mosley, who made eight starts last year and finished with 26 tackles and 2.5 sacks, will likely be a reserve. However, there's a chance he could push Earl Mitchell for the starting job.
Either way, Mosley (6 feet 2, 312 pounds) will be part of a rotation that includes reserves Anthony Johnson, a second-year player, and rookie Jordan Phillips, a second-round pick from Oklahoma.
Miami finished 24th in run defense last season and Detroit was No. 1. The Dolphins, who lost tackles Jared Odrick (free agency) and Randy Starks (released) during the offseason, have spent much of OTAs (Organized Team Activities) installing third-down, goal-line and red-zone defense.
Perhaps Mosley's acquisition means they saw a deficiency that needed to be addressed.
--Left tackle Jason Fox, the likely opening day starter while Branden Albert recovers from last season's knee injury, has been on the losing end of his battles with defensive end Olivier Vernon so far.
Granted, players aren't wearing pads, but it bears watching because Fox, a right tackle for most of his previous four NFL seasons, could be the opening day starter. And he acknowledges it's a bigger role protecting quarterback Ryan Tannehill's blind side.
"I think left side maybe the stakes are a little higher," Fox said. "It's Ryan's back side. And obviously you play a great player every game."
The Dolphins are hopeful that Albert will be ready for opening day. But they'll watch Fox closely. Last season, they switched right tackle Ja'Wuan James to left tackle when Albert was injured and inserted Fox at right tackle. But the Dolphins decided it'd be better to leave James at right tackle for the long term.
If Fox can hold down the position until Albert returns, it would go a long way toward keeping some degree of normalcy on an offensive line that's already struggling at both guard spots.