The Washington Redskins entered the offseason with a long list of needs but a clear-cut priority: beefing up the defense’s front seven. They did that successfully through the draft and free agency, but the team’s mission of shoring up its 3-4 defense suffered a big setback Friday morning.

Rookie defensive end Jarvis Jenkins, the Redskins’ second-round draft pick out of Clemson, had an early morning MRI exam and learned that he suffered a torn anterior cruciate ligament in Washington’s 34-31 loss at Baltimore on Thursday. Jenkins will be headed to the season-ending injured reserved list and will spend the next several months rehabilitating his right knee. 

“The good thing is that nowadays, an ACL surgery isn’t rocket science anymore. It’s more like changing a tire,” said Joe Flanagan, Jenkins’s agent. “And Jarvis is such a hard worker, that I know he’ll make a full recovery, and probably will be back on the shorter end of what is the normal recovery time for an ACL surgery.”

Trainers are waiting for swelling in the joint to subside, but Jenkins could undergo surgery to repair the torn ligament early next week.

“I’m gonna work harder than I’ve ever worked to get back,” he said via Twitter on Friday morning. “I love this game too much.”

The injury is not only a season-long setback for a player with a promising future, but it stunts the progress of defensive coordinator Jim Haslett’s revamped defensive line. Jenkins had started the past two preseason games in place of an injured Adam Carriker and had been one of the standout players in training camp. 

The Redskins plan to rotate five to six linemen, and Jenkins, a 6-foot-4, 325-pound defensive end, figured to play a prominent role at both the right and left end spots, as well as in the team’s nickel and goal-line packages. After fielding the league’s 31st-ranked defense a year ago, Haslett felt adding Jenkins, Stephen Bowen and Barry Cofield to a mix that already included Carriker and Kedric Golston finally gave Washington “a real formidable” defensive front.

“He’s got a chance to be really good,” linebacker London Fletcher said of Jenkins. “He’s powerful, and he’s got a great attitude. Just works hard.”

Just as important, the 23-year-old Jenkins figured to be a cornerstone of a unit Coach Mike Shanahan hopes to rely upon for years to come. The Redskins began the past two seasons with the oldest roster in the league, and the lack of youth was particularly glaring on the defensive side of the ball. But they parted ways with veterans such as Phillip Daniels and Vonnie Holliday, while spending their first two draft picks on players coaches felt were the perfect fit for Haslett’s scheme. Ryan Kerrigan, the team’s first-round choice out of Purdue, is slated to start at outside linebacker.

But Kerrigan missed several days of training camp with a bone bruise, and of the 12 players drafted in April, Jenkins was the one who especially opened eyes.

“I think he was doing fantastic and was on the fast track to starting as a rookie,” Flanagan said. “Any of the coaches would tell you that they were pleased with him. I don’t think this changes the long-term potential that he has to offer the Washington Redskins.”

While Carriker has been sidelined for the past week with flesh wounds on the back of his heels, Jenkins had seen added reps in both practice and in preseason games at Indianapolis and Baltimore. On the Ravens’ second offensive possession Thursday night, running back Ray Rice took a handoff and headed Jenkins’s way. Rice cut back, though, and Jenkins said he felt a pop in his right knee as he tried to plant his foot and change directions.

Following the game, Jenkins was on crutches in the locker room but remained hopeful the injury wouldn’t be too serious. It was an optimism to which his teammates had already grown accustomed.

“He’s got the talent, the skill you’d expect from someone drafted that high. But the thing about him is he’s always smiling,” Cofield said. “Coach [Jacob] Burney rides him. [Haslett] rides him. And he’s always just getting up for the next play, smiling, ready to get better. Not all young guys are like that. He’s had to come in early and stay late, and he’s always smiled through it.”

Now, with a promising rookie on the sidelines, the Redskins must address an opening that has been created along the line. With an open roster spot, the Redskins could bring in another defensive lineman to evaluate. But with the top free agents off the market, they may have to consider the options already under contract.  

Darrion Scott, a 6-foot-3, 310-pound sixth-year veteran, immediately took Jenkins’s place at left end Thursday and recorded one quarterback pressure, but didn’t have any tackles.

Doug Worthington, a 6-5, 292-pound second-year player, also lined up at the spot and recorded a tackle against the Ravens.

Washington's final preseason game is Thursday against Tampa Bay at FedEx Field.

Staff writers Mike Jones and Barry Svrluga contributed to this report.