Outside linebacker Randy Gregory, a potential top-10 NFL draft prospect, said Wednesday that he tested positive for marijuana in February at the scouting combine.

"I blame myself," Gregory told NFL.com in revealing the positive test. "And I know it sounds cliché, but there's really no one else I can blame."

Gregory, who starred at defensive end for Nebraska the past two seasons, admitted he has a lengthy history with marijuana, saying he began smoking after graduating from high school. He tested positive for the drug in January 2014 and April 2014 at Nebraska, according to the NFL.com report, and faced being kicked off the team had he failed a third test.

He said the positive test at the scouting combine resulted from high levels of the drug that lingered in his system even though he had not smoked marijuana since December.

"I was worse at Nebraska than I've ever been at any other time of my life," he told NFL.com. "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."

He said he now is focused on his "dream" of playing in the NFL.

"I don't wake up every day saying, I'd really love to go smoke," he said. "It's not a struggle for me every day (now), it really isn't. In the past, hell yeah, it's been a struggle. It really has been."

"I don't wake up every day saying, I'd really love to go smoke," Randy Gregory said. "It's not a struggle for me every day (now), it really isn't. In the past, hell yeah, it's been a struggle. It really has been." AP Photo/David J. Phillip

The positive test could send Gregory down draft charts. In their latest mock drafts, ESPN's Mel Kiper Jr. had Gregory going seventh overall to the Chicago Bears, while ESPN's Todd McShay had him going fifth to the Washington Redskins. McShay also ranked Gregory as the top outside linebacker in the draft.

"Am I worried? Yeah, I'm worried," Gregory told NFL.com. "At the same time, I'm confident. I know I'm going to be all right in the end."

He said he addressed his marijuana use with the 29 teams he talked to at the combine, prior to learning he had tested positive.

"Obviously this is new news -- that I failed the test at the combine -- but the fact that I've smoked in the past isn't a mystery," he said. "I've had conversations with (NFL) coaches. I believe we all have an understanding of why I did it. But I feel like I'm improving. I know I am."

Gregory maintained that he has not used drugs other than marijuana. He also said he has a new support system around him and is being regularly drug tested.

In addition, former New York Jets and Kansas City Chiefs coach Herm Edwards has agreed to mentor him, he said. (Edwards is an NFL analyst for ESPN.)

Gregory will enter the NFL in the first stage of the league's substance abuse program.

"[Marijuana] could end my career," he told NFL.com. "This incident right now is a step toward ending my career. The last thing I want to do is fail another drug test and be out of the league."