Johnny Manziel apologizes to A&M fans on Twitter, vows he'll 'be back'

Dominik: Manziel not worth the investment (1:19)

Jeremy Fowler and Mark Dominik explain why Johnny Manziel isn't even on the radar of NFL teams and his best shot at getting back to football is in the CFL. (1:19)

Johnny Manziel pledged to salvage something positive from his turbulent NFL career, telling his fans and followers on social media to mark his words that he will "be back."

The Heisman Trophy winner and former Texas A&M star quarterback, whose rise and fall has long been dominated by headlines about his off-the-field partying, tweeted on Monday to ask Aggies fans for forgiveness and express his love and devotion to the school.

Manziel, 23, was replying after being tagged in a tweet by an A&M blog featuring video of one of Manziel's touchdown runs against UTEP in 2013.

Manziel also posted a message on Instagram later Monday, assuring fans that his playing career isn't over and he can come back.

In an email to The Washington Post that was included as part of a larger profile of the quarterback published this past weekend, Manziel told the newspaper, "I'm actually doing well.

"I have good friends around me supporting what I do and I try to support them in what they want to do. I'm not saying I'm never drinking again, but for now just mostly being healthy. I've got a killer gym in my house and I can spend time working out. I'm interested in doing a lot of different things in my life -- including football -- but, right now, I'm just exploring options and waiting to see what the future holds."

The Cleveland Browns selected the player dubbed Johnny Football in 2014, but he struggled on the field and was released this year.

Since the 2015 season ended, two agents have cut ties with Manziel after demanding he get a second round of treatment for drug and alcohol use.

Manziel also faces a misdemeanor assault charge that carries a penalty of up to a year in jail and a $4,000 fine after he was accused of hitting and threatening former girlfriend Colleen Crowley during a night out in January.

Manziel also faces potential punishment from the NFL under tougher standards regarding domestic violence cases adopted in 2014, following former Baltimore Ravens running back Ray Rice's domestic violence case. However, Manziel is not currently with an NFL team and therefore is not subject to league policies.

The free-agent quarterback also was suspended for the first four games of next season for what a source told ESPN was a violation of the NFL's substance abuse policy. The suspension, announced last month, is not related to the league's domestic violence policy.

As the domestic assault case has played out, the 2012 Heisman winner has been photographed partying from Hollywood to Las Vegas to New York in recent months, and his family has expressed concern about his well-being.

Information from The Associated Press was used in this report.