OMAHA, Neb. - Defensive end Randy Gregory said he tested positive for marijuana at the NFL scouting combine last month and that he failed two drug tests at Nebraska last year.

Gregory disclosed his marijuana use in an interview with NFL Media on Wednesday.

Gregory went into February's scouting combine projected to be among the top 10 picks in the draft. He declared for the draft after his junior season at Nebraska, where he recorded 17 1/2 sacks in two seasons.

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He said he tested positive for marijuana at Nebraska in January 2014 and April 2014. Gregory said he hadn't smoked marijuana since December.

"I blame myself," Gregory told NFL Media. "And I know it sounds cliche, but there's really no one else I can blame."

Eddie Rhodman Jr., one of Gregory's handlers, said on Thursday that Gregory would not comment further.

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Gregory said he knows the failed drug tests could hurt his draft position.

"Am I worried? Yeah, I'm worried," he said. "At the same time, I'm confident. I know I'm going to be all right in the end."

Gregory, from Fishers, Indiana, played his freshman season at Arizona Western Community College in 2011 and missed 2012 because of a broken leg. He transferred to Nebraska in 2013.

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Gregory missed two games because of injury last year but was not suspended for any after testing positive twice at Nebraska. The school's drug policy was revised last October and now requires an athlete to be suspended for 10 percent of his team's contests after a second positive test.

"I was worse at Nebraska than I've ever been at any other time of my life," Gregory said of his marijuana use. "But I know how I am now. I think if teams really look at how I am now more so than the past, they'll see I'm making strides to get better, as a person and as a player."