LEXINGTON, Ky. — One of the key players in a Kentucky defense that expected to be heavy with experience will not be back with the Wildcats.

Athletics director Mitch Barnhart and defensive end Jeremy Jarmon announced at a media conference this morning that Jarmon had been ruled ineligible for his senior season by the NCAA.

Jarmon read from a prepared statement that he had inadvertently taken a banned substance, and tested positive during a random NCAA test in February. An appeal was denied, effectively ending Jarmon's college football career.

One of Jarmon's goals in the offseason had been to become leaner, he said. He bought a dietary supplement while shopping for vitamins on the recommendation of a worker at a nutrition store, not knowing that it contained a banned substance.

"I do not need to cheat to be successful," he said, reading from a prepared statement.

Jarmon did not specify what the substance was, or where he purchased it, and took no questions during the media conference.

Jarmon took the supplement while recovering from a shoulder injury and was not taking part in activities. He had been taking the supplement for 15 days before checking with the training staff, who told him to stop taking it.

"But it was too late," Jarmon said.

He tested positive for the substance in a test administered by the NCAA on Feb. 24, but tests results were negative six weeks later, Jarmon said.

Barnhart had hoped the NCAA would consider "extenuating circumstances" in Jarmon's case, and he had issues he would raise with the NCAA before talking about them publicly.

"The NCAA rules are the rules that we all live by and they're consistent, based on precedent and we've got to honor this," Barnhart said. "It may not always feel right, but there is precedent and it is consistent."

Jarmon, from Collierville, Tenn., could not hold back tears as he concluded his statement.

"My fans and teammates will be disappointed when news of this spreads," he said, "but no one can be more disappointed than me. ... I was born a Kentucky fan, I will die a Kentucky fan, I will be a Wildcat for life."

Barnhart hoped the bright spot out of Jarmon's situation would be that other athletes see the danger of taking supplements without knowing what they contain.

"The message is clear to other student-athletes, professional athletes, young high school athletes," he said. "If you don't know what it is, you can't take it."

Jarmon was projected to be one of five defensive starters returning to the team next season. Jarmon was one of three returning defensive starters, along with cornerback Trevard Lindley and linebacker Micah Johnson, who went through the NFL's evaluation process before returning to the Wildcats.

Johnson started in 12 games for Kentucky last season, making 38 tackles last season, including 4.5 sacks. He has 17.5 career sacks, third in Wildcats history. Jarmon was an honorable mention on last season's AP All-Southeastern Conference Team.

Jarmon has completed his degree in political science and is working on completing a second major.