It stands to reason that just about every position is affected when 15 players are out with injuries. But an entire starting unit down?

That's what the Cleveland Browns are dealing with at linebacker. Kaluka Maiava and rookies L.J. Fort and James-Michael Johnson lined up with the first team Sunday and Monday in 11-on-11 drills. Starters Scott Fujita, D'Qwell Jackson and Chris Gocong are sidelined. The latter is gone for the season with a torn Achilles.

Coach Pat Shurmur reacted negatively when asked if he's concerned with the spate of injuries that have befallen his team. He said simply that the backups must take advantage of their opportunities. And on Monday he expressed satisfaction with the work of Fort, an undrafted free agent who has soared up the depth chart.

"He's had an excellent camp," Shurmur said. "When we left in June I was looking forward to when the linebackers could put their pads on. [Fort] has done a good job on scrimmage snaps and in special teams. ... He has good instinct, he's the right size (6-foot, 230 pounds) and has a powerful build."

Shurmur added though Fort has played extensively in the middle, he can also work the outside.

That's where Johnson fits in. The fourth-round pick would probably start if the season began today if Fujita is indeed suspended for the first four games for his alleged role in Bountygate. Johnson scoffs at the notion that the NFL represents a huge jump for a rookie. His belief was confirmed in the preseason opener Friday night in Detroit. He claims he did not feel overwhelmed playing in his first NFL game.

"That brought out the feeling that I can play in the NFL --it's not that much different than college," he said. "People think it is, but it's not. I still have to work on my technique, my run fits, my man-to-man coverage. I can definitely get better."

He might need to in a hurry. But the injuries that have provided him with an opportunity to compete with the first team have not instilled in Johnson a sense of urgency to adapt to the pro game. His motivation has come from within.

"I'm trying to get up to speed regardless," he said. "I'm trying to get better every day than I was the day before."

He has gained knowledge from the veterans more by watching them perform than by verbal communication.

"I see how meticulously they do all their details of their work," he said. "I try to mimic them."

Johnson is the most athletic of the three, which could work to his advantage. The Browns have been painfully slow at linebacker in recent years. They are also desperate for an outside pass rusher aside from DE Jabaal Sheard. But Johnson was not known for his ability to blitz or track down quarterbacks in the University of Nevada. He managed just 7.5 sacks in four years, including 1 1/2 during a senior season in which he recorded 100 tackles.

Stay dialed in on the Cleveland Browns on Twitter at @CBSSportsNFLCLE throughout the season with on-site updates from CBSSports.com RapidReports correspondent Marty Gitlin.