Ryan Leaf's May Arrest Not Substance Abuse Related, Lawyer Says

Ryan Leaf's domestic battery arrest was NOT substance abuse-related ... so says the ex-NFL QB's attorney, who tells TMZ Sports the former San Diego Charger is still "100% sober."

There had been some concern after 44-year-old Leaf -- who has battled drug and alcohol problems in the past -- had suffered a relapse that led to his arrest on May 22.

But, when we spoke to David Greenberg of the Law Offices of Soda & Greenberg ... he told us that just wasn't the case at all.

"He is 100% totally sober," Greenberg said of Leaf, "and spends a good part of every day over the last five years helping other people remain that way."

In fact, Greenberg says the whole alleged incident was nothing more than a "minor dispute."

"Nobody was injured," Greenberg said. "There was no allegation of any kind of weapon or anything like that."

"This was a couple that had a small minor dispute and it's unfortunate that it ended up in the criminal justice system."

We broke the story ... Leaf was booked on a domestic battery charge at around 2 p.m. on May 22 -- and was formally hit with two misdemeanor charges by prosecutors this week.

But, Leaf cut a plea deal in court Friday ... and ultimately avoided further jail time in the case.

Greenberg said Leaf and his family are happy to have all this now behind them ... adding Ryan is still committed to helping people with substance abuse problems daily.