Rosenhaus, one of the most prominent sports agents in the United States, said Wednesday he believes the free agent quarterback needs treatment.
The agent issued a statement that said he conditionally terminated his agreement with Manziel, who was released last month by the Cleveland Browns
"I have informed him that if he takes the immediate steps I have outlined for him that I will rescind the termination and continue to represent him," said Rosenhaus, who became Manziel's agent after Cleveland let him go.
Rosenhaus didn't say why he believes Manziel needs treatment, which would be his second time in a facility.
In February 2015, Brad Beckworth, a friend and adviser to Manziel and his family, said in a statement that the quarterback entered a treatment facility the previous month. Manziel was at Caron, an alcohol and drug treatment facility in Pennsylvania.
"I owe private apologies to a lot of people that I disappointed but a very public one to the Browns organization and the fans that I let down," Manziel said in a statement last April 17 after leaving rehab. "I take full responsibility for my actions and it's my intention to work very hard to regain everyone's trust and respect."
Manziel was involved in a curious incident over the weekend in Los Angeles.
He was riding Saturday night in a car driven by Ryan Silverstein, Los Angeles police said, when the vehicle crashed into a light pole. Silverstein and his passengers ran from the scene, Officer Liliana Preciado said. They later returned to the accident site and Silverstein, who works for rapper Drake, admitted to driving too fast, Preciado said.
No one was hurt.
In a video posted by TMZ earlier this week, Manziel told paparazzi that he has been hanging out in Los Angeles but hasn't been getting drunk or out of control. TMZ said the video was recorded the night of the single-car accident.
Manziel entered the national spotlight as a redshirt freshman at Texas A&M, leading the Aggies to a 29-24 upset win against No. 1 Alabama in November 2012. The next month, he made history as the first freshman to win the Heisman Trophy, college football's most prestigious award.
Last season, Manziel appeared in nine games for the Browns, starting six. He threw for 1,500 yards and seven touchdowns and five interceptions. He rushed for 230 yards.
His first agent, Erik Burkhardt, dropped Manziel after the season ended in early February.
Rosenhaus' agency has about 80 NFL clients, according to a Sports Business Journal report in October, more than any other agent.