Cleveland Browns quarterback Johnny Manziel entered rehabilitation treatment last Wednesday, adviser Brad Beckworth told ESPN on Monday. 

"Johnny knows there are areas in which he needs to improve in order to be a better family member, friend and teammate, and he thought the offseason was the right time to take this step," Beckworth said, according to the site. 

"On behalf of Johnny and his family, we're asking for privacy until he rejoins the team in Cleveland."

Although Manziel nor Beckworth have revealed an official reason for the rehabilitation treatment, rumors have already surfaced claiming that substance abuse may be responsible. The Cleveland Browns quarterback is said to have shown a continuos pattern of lack of dedication to his sport and more interest in nightlife. 

Last December, Manziel failed to show up for his team's walk-through prior to the final game of the season. 

A source close to the player said security found Manziel "drunk off his a--," adding that he was not present all morning, ESPN also reports. 

"I brought this on myself," Manziel said during a press conference following the end of the season. 

"I brought these cameras and all these people that are in this locker room right now, and I don't think it's fair to myself, I don't think it's fair to anybody in this locker room the distractions I've brought at points in time."