"I was working out in Atlanta with a doctor and he gave me some supplements. I took them. That's the gist of it. Apparently, there was something in it that wasn't supposed to be in there. Plain and simple," he said.
"It was the first time in my career I've taken supplements from anybody," he said.
And the last time.
"I won't take nothing. If I don't take anything, I won't have to worry about it. One and done," he said.
He said he'll now eat "a bunch of steaks" to get protein.
Stroud said he was concerned about what the incident would do to his reputation.
"I didn't want people to think I was a cheater. I have been doing this (playing football) long without it. I feel like I've been playing at a high level. I don't have to (use steroids). God gave me this talent to play football and I feel like I do it well. I don't need no juice or anything to help me," he said.
Stroud didn't identify the doctor and said he didn't want to point fingers at anybody.
"I made a mistake. It's on me. It's my responsibility. All the stuff was stuff out of any nutrition store. It wasn't like I was going online and going to the Orlando pharmacy and all that stuff," he said.
That was a reference to two Orlando pharmacies that were raided by federal agents in March amid allegations that they sold steroids on the Internet.
The NFL's position is that if the player tests positive for steroids, it doesn't matter whether or not he knowingly took it. The players are responsible for anything they ingest and they put out a booklet of supplements that are allowed.
Stroud said his supplements were on that list.
"As far as I knew, the stuff was good," he said because the substance was included in the booklet.
"But those things aren't regulated and there could be something in there they don't put on the bottle (label). I think that's what happened to me. It's water under the bridge. Now it's time to play ball," he said.
Stroud now hopes to help the team's push for a wild-card spot.
"I'm going to do whatever is going to help this (team) get in the playoffs," he said.
Stroud was not allowed to be at the Jaguars' facility during the suspension and it was difficult for him not to be with his teammates. He was playing dominoes with some teammates Wednesday in the locker room.
"When you're the only one home, it's boring because all your friends are working. They look like they're having a great time on the field and I have to watch from afar. That's probably the toughest thing. Anything you love and care about and you're not able to do it, it gets to you," he said.
Stroud, who underwent microfracture surgery on his ankle in the offseason, also feels he can still play at a Pro Bowl level. He said before he was suspended that his statistics were similar to ones compiled by Tennessee's Albert Haynesworth
"and the other tackles that you guys are calling dominating."
Stroud added, "Hopefully, I can go out there and show glimpses of the old Marcus."
Jaguars defensive end Marcus Stroud has decided he'll no longer take any kind of supplements. Stroud, who served a four-game suspension for testing positive for steroids that ended Monday, said the positive test was apparently the result of tainted over-the-counter supplements and he'll never use them again. Here's what he said: