In the final week of the preseason, every NFL team is trying to map out the bottom of its regular-season roster, coming to terms with just how much depth it will or won’t have at every position. At no spot is depth more crucial, perhaps, than along the defensive line.

The Redskins were particularly thin on the line during the team’s first season running a 3-4 defensive front, but coaches are more comfortable this year with their talent level, even after the loss rookie of Jarvis Jenkins last week to a season-ending anterior cruciate ligament tear.

“We feel good about the group we have,” said defensive coordinator Jim Haslett. “It’s a shame that we lose a guy like Jarvis. but these guys will step up and play well.”

They had better. The success of the Redskins’ defense, the 31st-ranked unit in the league a year ago, could hinge on the depth of the line. More players rotate in along the defensive line than any other position. The offensive line switches personnel only when there’s an injury or an urgent need. Linebackers and defensive backs play most every down. But Haslett might send in a new lineman or two on each snap.

There’s little guesswork involved. Just like baseball managers monitor a starter’s pitch count, defensive coaches paying close attention to how many snaps each lineman plays.

“We have an idea of what they should play game to game,” Haslett said, “and really for the whole year, we have an idea of how many they should play.”

Take last year’s midseason game against Green Bay, for example, before injuries started to pile up. The Redskins used seven different defensive linemen: Vonnie Holliday played 29 snaps, Adam Carriker played 28, Kedric Golston 26, Maake Kemoeatu 19, Phillip Daniels 11, Albert Haynesworth 8 and Jeremy Jarmon 7.

In some games, a defensive end might play as many as 40 snaps — usually well more than the team’s nose tackle. In Washington’s first meeting against Philadelphia last year, Golston and Carriker played 41 and 33 snaps, respectively, while Kemoeatu played 19 and Haynesworth 30, many in the team’s third-down nickel formations.

“The nose position gets the most physical in there,” Haslett said. "You have to be careful what the numbers are.”

The Redskins still will rotate heavily, even though coaches believe they have a higher level of talent this season. Washington carried eight defensive linemen into Week 1 last season, five of whom are gone this year. Carriker, Golston and Anthony Bryant were brought back, while Daniels and Kemoeatu were released and Haynesworth, Jarmon and Holliday were traded.

The players they’ve added — highlighted by free agents Stephen Bowen and Barry Cofield — know that even the best defensive linemen will spend time on the sideline. Bowen played most third-down snaps in the Dallas Cowboys’ 3-4 defense a season ago, rotating in on first and second downs.

“If there were 60 plays, I may have played like 27 and Igor [Olshansky] or somebody might’ve played 37,” Bowen said. “It was kind of even. We had a pretty good rotation going. Kept guys fresh, just ready to come off the ball.”

Depth particularly reveals itself late in the season. Carriker was the only lineman to start all 16 games a year ago.

“The last three games last year, it was pretty much just me and Vonnie left,” he said. “We barely got off the field. It wasn’t bad to do in three games. But people tend to break down, people tend to get hurt. Over a 16-game season, that's why you rotate, to keep guys fresh.”

The effects usually can be seen over the course of a single game too. If coaches can give their linemen breathers in the first half, they still may have energy for the final quarter.

The challenge facing the Redskins will be identifying the linemen for the rotation and determining how to spread out the snaps. They had hoped to use Jenkins at both ends, as well as in nickel packages. Entering Thursday’s preseason game against Tampa Bay, coaches don’t seem concerned.

“We’ve got some depth at that position,” Coach Mike Shanahan said.

With Jenkins lost for the season, Carriker’s spot as the starting left end should be safe. Cofield will play nose and Bowen will see the majority of snaps on the right side side.

Bryant will back-up Cofield at nose tackle, and Golston and Darrion Scott will play the end positions. Jenkins’s injury also may have created a spot for Doug Worthington, a seventh-round pick by Pittsburgh in 2010. After the Steelers released him, Worthington spent part of the year on Tampa Bay's practice squad and signed with the Redskins on Aug. 7. He’s still adjusting to a 3-4 scheme, but feels he’s a good fit.

“I think that’s what I was built for, long arms, taller guy. . . It took me a few days, coming from Tampa, being that 4-3 defensive tackle — getting off the ball, running, chasing and things of that nature,” Worthington said, “I actually had to slow myself down a little bit and put my feet in the ground more.”

Worthington is a single puzzle piece. For the Redskins to thrive, they need all the linemen to contribute.