When Mike Shanahan opened his first training camp in Washington, the Redskins’ running backs were a punch line of sorts in NFL circles. Clinton Portis, Larry Johnson, Willie Parker — it wasn’t a running back-by-committee as much as a senior citizens committee.

“Experience and inexperience,” is how running backs coach Bobby Turner describes the difference this season. “Last year, we had a bunch of guys that had household names, that had played a lot. This year is different.”

Gone are the three 1,000-yard rushers. Instead, the Redskins will rely largely on unproven runners, players who coaches are confident can improve upon last season’s dismal numbers. The upgrade isn’t flashy, but team officials think it will be noticeable.

“It takes a while to implement your system,” Shanahan said. “Going into your second year is so much different than your first. People understand the principles of what you’re trying to do, they understand better who is there and what their capabilities are. So the difference between your first year and second year in the running game is night and day.”

The Redskins ranked 30th in the league last season, averaging 91 yards on the ground. In Shanahan’s 14 years in Denver, his worst rushing team still managed to average 116.4 yards per game.

For the past seven seasons, the Redskins relied on Portis and fullback Mike Sellers in the backfield. Portis, though, was given his walking papers in February and it appears Sellers’s best chance of making the team will be as a blocking tight end.

Instead, the Redskins seem prepared to use Ryan Torain, an injury-plagued third-year tailback, and fullback Darrel Young, a converted linebacker. The Redskins have added a few new faces, too, with the intention of providing depth and a change of pace in the backfield.

The team acquired Tim Hightower in a trade with Arizona on Sunday. The fourth-year veteran could challenge Torain for the starting job — but might be more likely to serve as a third-down back.

“I like everything about him. . . . We believe that we have a back that can do it all,” Shanahan said. “He can run, he can pass-protect, he’s a third-down back. I feel good having him here.”

Hightower, who could be in uniform with the Redskins by Tuesday morning, started the past 21 / 2 years in Arizona and is particularly adept at pass protection. He’s well-versed in picking up the blitz and instantly becomes Washington’s top blocker among the tailbacks.

Perhaps most importantly, Hightower will provide some insurance in case Torain isn’t up to the challenge of playing a full season — an even-money bet most years. Torain has been plagued by injuries since college and was slowed by an ailing hamstring last season.

“Ryan has some competition,” Shanahan said. He “hasn’t been able to stay healthy.”

Still, Torain was the lone Redskins rusher to tally more than 300 yards in 2010. He accounted for all three of Washington’s 100-yard games, finishing the year with 742 yards, an average of 4.5 yards per carry. The Redskins would love for him to duplicate that pace, but he has to stay in the lineup.

Because of injures, the team had to rely on three starting tailbacks a year ago. As the season wore on, struggles increased for the offensive line and its limping running game. The Redskins topped 80 yards rushing just once in the final six games of the season.

“I was happy with my performance, but I wish I was out there for 16 games,” Torain said.

In parting ways with Portis, who was consistent on the field if not always predictable off it, the Redskins knew they needed to get younger. They drafted two running backs: Roy Helu, a fourth-rounder from Nebraska, and Penn State’s Evan Royster, a Westfield High product who was picked up in the sixth round. Helu, especially, has looked impressive in the early days of training camp, showing a burst of speed and some flashy moves in the open field.

Torain knows that even though he’s lining up with the first team right now, he has little job security.

“We’re never comfortable. We always got competition,” said Torain, a Shanahan draft pick in Denver who started last season on Washington’s practice squad. “Coach is going to play the best back. So I just have to keep working hard.”

Sellers, too, was a mainstay in the backfield, blocking for Portis. But he’s spent the early days of training camp solely with the tight ends. Young, a second-year player who was an undrafted free agent out of Villanova, has been playing fullback with the first string.

Keiland Williams also has been seeing some snaps at fullback. The second-year LSU product started three games last year at tailback, highlighted by his 89-yard, two-touchdown performance against Philadelphia. But with a crowded backfield in camp, he knows he might have to diversify his skills to make the 53-man roster.

“I want to help my team as much as I possibly can,” said Williams, a strong blocker and pass-catcher who served as the team’s top third-down back a year ago. “If it’s at the fullback spot, I’m willing to do that. If it’s at the tailback spot, I’m willing to do that, as well.

It didn’t take too many training camp practices to learn the difference in the two positions — about two yards and a blink of an eye.

“At tailback you’re seven yards deep. At fullback you’re five yards deep, so everything happens a little faster,” Williams said, “and you’re banging a little bit more. But I think that’s something that I’ve shown, that I can handle contact and I’m willing to hit. So I think that’s another reason they put me at this spot.”

Staff writer Shemar Woods contributed to this report.