Indianapolis Colts veterans Vick Ballard and Donald Thomas have had trouble staying healthy in recent years and on Tuesday, general manager Ryan Grigson acknowledged the pair's lack of practice time in the preseason may have an impact on their ability to make the 53-man roster.

"It's tough," Grigson said, via ESPN's Mike Wells. "There is no other way to slice it. We have to be able to at some point be able to compare them to other people at their position group and the only way to do that is by playing football, by practicing and being out there and competing. It's a tough spot for any of these guys. I think and I feel for them. I have been there before. It's no fun to not be out there. They also have to be 100 percent healthy, otherwise it makes no sense throwing them out there to get re-injured."

Thomas, a veteran guard, is still on the team's physically unable to perform list. The 29-year-old has played in just two games over the last two seasons due to a torn quad and a torn bicep.

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Ballard, who led the Colts in rushing in 2012, also sat out almost all of the past two seasons. The 25-year-old missed all but one game in 2013 with a torn ACL and missed all of last year with a torn Achilles. He recently returned to practice after missing a week with a hamstring injury.

(h/t ESPN)