Thomas' first two seasons weren't exactly dazzling, but the Dolphins obviously thought a lot of his potential. As for Thomas himself, he's not ready to concede anything to Miller.
I asked Thomas directly on Wednesday how he would assess his chances of becoming the starter at halfback.
"Very good," Thomas answered. "I feel like I don't take a back seat to anybody. I'm just going to keep working and I feel like if I stay healthy I'll be good."
Thomas started two games in his rookie season when he appeared in 13 games and rushed for 581 yards. He rushed for 325 yards in 12 games in 2012 but never started.
While he had his moments in those two seasons, highlighted by a 107-yard performance against Houston in 2011, Thomas has averaged only 3.5 yards as an NFL player and has fumbled five times.
Thomas says his biggest issue has been injuries.
"I wasn't on the field, I missed a lot of games and when I was on the field I don't think I was the same guy," Thomas said. "So I'm just going to continue to work.
"I don't think it's conditioning because I'm always in good shape and I work hard off the field as well. I was just a lot of bad luck."
It's not surprising, then, that Thomas said the biggest thing he needs to do to improve as a running back in his third season is stay healthy.
Thomas says he was happy with his work as a blocker in his first two seasons and is hopeful that will give him an edge in the battle to replace Bush as the starting running back.
Not that there are many fans or observers outside the team's facility who think he has much of a chance to beat out Miller.
"I'm not worried about what everybody is thinking outside of our locker room," Thomas said. "It's all about what the coaches see and what I do on the field. I'm just going to continue to work hard and at the end of the day that's all I can do."
With the Dolphins having completed only four of their training camp practices, it's way too early to gauge whether anyone has jumped out at the position, although Miller has been the one lining up with the first-team offense.
That said, Thomas is happy with what he's done so far this summer.
"I feel ike I've been running hard and picking up my blitzes, but it's only the second practice (in pads)," he said. "So I'm only going to get better."