ALLEN PARK, Mich. -- Travis Lewis says it all started because of a mistake, the first failed drug test of his life that led to a four-game suspension for taking Adderall, which is on the NFL’s list of banned performance enhancing drugs.

It cost him the final four games of the Detroit Lions' regular season and more than $100,000.

“I wasn’t aware of what I was taking and made a mistake,” Lewis said Monday, the first time he was in the Lions' locker room since the suspension. “First drug test I’ve ever failed in my entire life. So you learn from it and you move on.”

He chose not to appeal the ruling, took his suspension and the linebacker will be eligible to return next season for the Lions.

Lewis said he got the Adderall from a friend who had told him he was taking caffeine pills. He wasn’t and found out two or three weeks before the suspension came down that he had failed a drug test.

Now, he said, that person is no longer his friend and he learned not to trust anyone except himself when it comes to what he will put in his own body.

“Definitely,” Lewis said. “Former friend that cost me a lot of money and games that I’ll never be able to get back.”

Lewis was a seventh-round draft pick in 2012 and has played primarily on special teams in his NFL career. When Lewis was suspended, the Lions signed linebacker Julian Stanford in his place.