Memphis Grizzlies guard O.J. Mayo says he believes an “energy drink” he bought at a gas station contained the substance that led to his 10-game suspension for violating the NBA’s drug policy.

Mayo was jovial and smiling as he spoke about his suspension for the first time Saturday before the Grizzlies’ game against the Washington Wizards, taking questions from reporters on the team’s practice court.

But he wouldn’t get too specific.

“I didn’t know it had any bad substances in it, and it caused a 10-game suspension …,” Mayo said. “It’s not like I went to a GNC and got some Muscle Armor or ordered some supplement off the Internet or anything. It was just a local gas station that kind of got me hemmed up.”

The NBA suspended Mayo on Thursday for testing positive for dehydroepiandrosterone (DHEA), which is on the league’s list of banned performance-enhancing drugs. His suspension started Friday night at Philadelphia, and he will be eligible to return Feb. 15, also against the 76ers in Memphis.

Mayo spoke and then had to leave the arena at least two hours before tipoff. The Grizzlies are holding O.J. Mayo bobblehead night in honor of the No. 3 pick overall in the 2008 draft.

Mayo’s third season has been rough and almost seems to be unraveling after he opened his NBA career as runner-up to Derrick Rose of Chicago for Rookie of the Year.

Mayo lost his starting position in November, has been in a fight with a teammate when he refused to pay up after losing at cards during a team charter and had to deal with off-court family issues.

He’s averaging 12.2 points a game and playing 28.8 minutes. Not what was envisioned for the phenom who was one-and-done at Southern California. After he left USC, the Trojans were hit with NCAA sanctions when it was determined that Mayo received improper benefits.

His troubles this season started Nov. 20 when he was late for a game-day shootaround, leading coach Lionel Hollins to take him out of the starting lineup against the Miami Heat.

Since then, the 6-foot-4 Mayo has come off the bench in a move made ostensibly to bolster the scoring and energy among the reserves.

“Moving to the bench, I thought it was a benefit for the team,” Mayo said. “Me and (Hollins) talked about it at length, and it seemed to work out for our team.”

Off the court, Mayo’s father, Kenneth Maurice Ziegler, 39, was charged Dec. 23 with attempted murder after he hit a police officer with his car and dragged him for several feet in Huntingdon, W.Va.

Mayo has declined to comment on the arrest. He didn’t live with his father growing up, but Ziegler did help Mayo’s mother, Alisha Mayo, hand out turkeys and hams in Huntingdon on Mayo’s behalf in November.

After the Grizzlies’ Jan. 2 victory over the Los Angeles Lakers, Mayo was involved in a fight with teammate Tony Allen over a debt from an in-flight card game on the team’s return from the West Coast.

Mayo missed the next game at home against Oklahoma City. The team said the reason was bronchitis.

But Mayo also had visible facial injuries from the fight when he joked with Allen a couple days later. The fight prompted the Grizzlies to ban gambling on team flights.

His play and shooting had been inconsistent since. He missed all four of his shots in Wednesday’s loss at New Jersey. That marked the first time in his career Mayo was held scoreless.

If all of that wasn’t enough, Mayo has been mentioned in trade rumors often.

And now this.

Mayo said Saturday he was unaware the over-the-counter product contained a substance banned by the league. Asked if he understood how people question that when athletes work so hard on their bodies, Mayo said he probably could ask any NBA athlete about DHEA and didn’t think he’d get an answer.

“There are just so many substances that are considered banned substances because in some way it could help your performance on the court,” Mayo said. “As athletes, we should be responsible for what we put in our bodies. I understand that.”

NBA players are subject to four random samples each season. Mayo said there were suspicions with his first sample taken in mid-November. The league called him in early-December to tell him they were going to test his alternate sample from that time, leading to the suspension.

“I’m not going to say everything has been gravy,” Mayo said. “But guys have to rally up without me, and they’re doing a great job. “We’re 2-0 when I don’t play. So, if we can get wins when I don’t, I won’t mind in a way.”