EARTH CITY, Mo. --With running back Isaiah Pead out for the season because of a torn anterior cruciate ligament in his left knee, the St. Louis Rams could have a different look on their roster when cutdown day arrives.

To be clear, Pead was in a battle for a roster spot as he worked primarily on special teams with occasional contributions to the offense. That was the role he was fighting for and though it wasn't a huge role, it was clear that was his route to the roster.

"He worked very very hard to get in the position to where he was a very productive special teamer for us and we had high hopes for him doing some things out of the backfield for us as well," Rams coach Jeff Fisher said earlier this week.

Pead is expected to go on injured reserve sooner than later as he'll miss the season following upcoming surgery. The trickle-down effect of his loss won't be noticeable immediately in the sense that there isn't a pressing need to add another running back.

Where Pead's loss will be worth following is how it changes the team's 53-man roster composition. Last year, the Rams kept five running backs coming out of the preseason, including Pead, Daryl Richardson, Zac Stacy, Benny Cunningham and Chase Reynolds. Reynolds played exclusively on special teams and though Pead would have done a bit more than that, he likely would have been primarily used there as well.

Without Pead, the Rams now have five running backs on the roster. Stacy, Cunningham and rookie Tre Mason are all but locks to make the team. Without Pead, Reynolds would seem to be in prime position to return as a core special teams player. Theoretically, the door is also open for undrafted rookie Trey Watts should the Rams want to keep five backs again.

Watts has impressed when healthy though he has missed parts of camp because of a hamstring injury. But he had a solid outing against Green Bay last week, rushing for 19 yards on three carries. He'll also get opportunities to help on special teams.

“We’re going to allow him to get significantly more carries over the next couple weeks," Fisher said. "We want to see what he can do. Now, he’s been slowed by the hamstring, so he’s missed time, but he’s back on the practice field. He had a number of special teams reps in the game and did well. He can run, and so yes it opens a door. Now, it doesn’t necessarily mean, there’s no guarantees just because we kept five last year, means we’re going to keep five this year. We may use that spot at another position where there’s maybe depth, but it’s certainly going to give him an opportunity.”

Therein lies the rub. Not many teams carry five running backs and if the Rams don't they could add extra depth at a spot like the offensive line, where they've gone heavy with numbers in the recent past. It could also open the door for a sixth cornerback, a fifth safety or even an extra linebacker. It also could even create an opportunity for the Rams to go with an extra defensive lineman.

While Ethan Westbrooks and Michael Sam appear to be dueling for a potential ninth roster spot on the defensive line, there might even be a window for a 10th.

That would be a departure from the past two seasons when they've kept nine, but it's also not outrageous given the talent they have in the group. Defensive tackles Deantre Harlan and Matt Conrath and end Sammy Brown also should be mentioned in that discussion.

All of that still has to play out, but it's clear the Rams will have much to consider when it comes time to put together their initial 53-man roster.