CLEVELAND -- Browns quarterback Johnny Manziel entered treatment on Wednesday, adviser Brad Beckworth told ESPN.com 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.

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

Manziel is expected to be in rehab at least a few weeks, but the amount of time depends largely on what doctors recommend, according to a source close to Manziel.

A source said the Browns are tentatively expecting Manziel to participate in training camp but are not placing any timetables on other offseason activities as he works through the treatment process.

The quarterback is voluntarily entering treatment as a direct result of his lifestyle away from the field, and he informed people in his circle last week that he wants to "figure out his value system," a source said.

A source told ESPN's Darren Rovell that a casino in Las Vegas offered Manziel six figures to host a Super Bowl party, but he declined.

Browns general manager Ray Farmer said in a statement that the team supports Manziel's decision.