The Redskins will get an extended look at both rookie running backs over the final two preseason games to determine if one or both are deserving of a roster spot after cuts.

With Matt Jones sidelined for the remainder of the preseason, the Redskins will give the "lion's share of the carries" to rookies Robert Kelley and Keith Marshall.

That means not only work with the second- and third-team offensive units, but with the starters as well.

"It will be interesting to watch these guys," Redskins head coach Jay Gruden said. "These guys have shown a lot of promise in training camp. We want to see them in game situations against a good Buffalo team and it will be a good test for them. Good for everybody."

Marshall was one of two seventh round picks by the Redskins in the 2016 NFL Draft. He's known for his breakaway speed and ability to fool defenders, but he simply hasn't had the chance yet to prove either quality.

Through the Redskins' first two preseason games, Marshall has collected just 25 rushing yards on 15 carries. But more carries will likely mean more chances to get loose in open space.

Kelley, meanwhile, leads Washington in rushing as he's collected 48 rushing yards on 10 carries with the team's only rushing touchdown to date.

"Great skillsets," said Chris Thompson, who believes he'll remain in the third-down back role even with Jones out. "They're young guys so there's some things here and there in the passing game where they get nervous about certain things and certain protections. As this preseason keeps going on, I keep seeing them getting better and better. We get them some work in these next two games and then the coaches make their decisions and we go from there."

Both, however, have never played against an NFL first-team defensive unit outside of practice against teammates who only wrap up but don't tackle.

At some point, though, your number will be called for an increased role. That was the case for 2012 fourth-round pick Kirk Cousins.

Cousins worked with the first-team offensive unit throughout the 2013 preseason while former Redskins quarterback Robert Griffin III was still recovering from an injury.

Then last season, he jumped into the No. 1 quarterback role for good.

"It's really good work for them to be able to get out there with the ones, against the ones, and have to perform play in and play out," Cousins said. "I think it's going to help challenge them. There were times for me as a first-, second- or even third-year player where I was kind of pushed into action and it stretches you as a player. It's going to get you to where you need to be that much faster. I think it's a really good thing for them. There may be some growing pains here and there, but that's what the preseason is for – to see what they can do, what they can't do."

Even though Jones will have to be a spectator for the Redskins' matchups with the Buffalo Bills and Tampa Bay Buccaneers, he'll be pushing Kelley and Marshall from afar.

Since offseason workouts, the running backs have tried to outdo each other in terms of who collects the most explosive runs.

"I know in OTA's I was beating [Matt], but when we got to camp he pulled away from me a little. I think I'll get him now while he's out," Kelley said with a smile.