ENGLEWOOD, Colo. - His scary spinal injury behind him along with the ill-fitting 4-3 defence, Derek Wolfe couldn't wait for the 2015 season to get here.

He won't be on the field now when it does.

The NFL informed the Denver Broncos on Friday that Wolfe would be suspended for the first month of the season for violating the league's policy on performance enhancing substances.

In a statement, the fourth-year pro offered his "most sincere apology" to the organization, his teammates and fans and insisted he took medicine this off-season that he didn't realize was banned.

"The medication is not a substance which would enhance my on field performance in any way and I genuinely was unaware that it was prohibited, but players are responsible for what is in their bodies," Wolfe said in a statement. "I will certainly exercise far greater caution in the future and will seek advice relating to the permissibility of any and all medications."

Losing one of their starting defensive ends is a big blow to a defence that's already dealing with big question marks at middle linebacker — the fulcrum of Wade Phillips' 3-4 scheme — as Danny Trevathan (knee) and Brandon Marshall (foot) are returning from surgeries.

During Wolfe's absence, the Broncos will rely more heavily upon veterans Malik Jackson and newcomer Vance Walker, who played for the Chiefs last season. Wolfe's suspension also could benefit second-year pro Kenny Anunike.

Wolfe can practice during training camp and play in the preseason before his Sept. 5-Oct. 5 banishment. He'll miss games against some elite running backs, including Baltimore's Justin Forsett, Kansas City's Jamaal Charles and Minnesota's Adrian Peterson. That puts added pressure on safety T.J. Ward and outside linebackers Von Miller, DeMarcus Ware and first-round pick Shane Ray to stop the run.

Wolfe played in every game last year, contributing to a Denver defensive line that allowed 79.8 rushing yards per game, the lowest single-season figure in team history.

He said this spring, however, that he was just a shell of himself in 2014 after missing a good chunk of the previous season, which was marked by a seizure on the team bus. Doctors believe that was related to a bruised spinal cord he suffered that preseason.

Wolfe hasn't played a true 3-4 — with three down linemen and four linebackers — since his days at the University of Cincinnati. He said this off-season he was actually surprised the Broncos drafted him in 2012. After all, the old coaching staff preferred playing four down linemen and three linebackers most of the time.

Wolfe said the 3-4 suits him because "I'm not really a speed rusher, I'm not really a big 330-pound defensive tackle, either. I'm kind of a 'tweener and that's really what you need at the 3-4."

Wolfe is back up to 285 pounds after regaining all of the 30 pounds he lost in 2013.

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