Leaf was arrested Friday in his hometown of Great Falls on burglary and drug possession charges, police said.
James Farren, the Randall County district attorney who prosecuted Leaf in Texas and negotiated a plea deal with him in 2010, said he would file the motion Monday to revoke the 10-year probation Leaf got in the agreement.
"I think it's sad," Farren said of the allegations against Leaf in Montana. "While I hoped for better results I'm not surprised it happened."
Leaf did not immediately respond to text and voice mail messages left Saturday.
The circumstances surrounding Leaf's arrest were not immediately clear. Great Falls Police Sgt. Dean Bennett, who confirmed Leaf's arrest, said Friday night that he had not seen a report detailing the allegations against the ex-football player.
Leaf was booked on felony charges of burglary of a residence and criminal possession of dangerous drugs, plus a first-time charge of misdemeanor theft, Cascade County Detention Center Officer Robert Rivera said.
Leaf was freed on $76,000 bond and is scheduled to make an initial court appearance Monday.
Leaf's defense attorney in the Texas case, Bill Kelly, said Saturday that he hadn't spoken to his client. Leaf's father, John Leaf, called Kelly on Friday to tell him about the arrest, he said.
"His dad was pretty upset, of course," Kelly said. "People get hooked on these things and it's hard to get off of them. It's just a sad, sad deal because he was doing so well."
Leaf, a former standout quarterback for Washington State, was the No. 2 pick in the 1998 draft behind Peyton Manning. But Leaf flamed out as quarterback for the San Diego Chargers, gaining a reputation as one of the biggest busts in NFL history.
A message left at his parents' house was not immediately returned Friday night.
Leaf released a statement through his publicist, Wendy Ogunsemore on Friday night.
"I've made some mistakes, and have no excuses," the statement read. "I am using the tools I've learned to move forward rather than backwards, and will be open to talking about the details in the days to come. I am confident that there will be further understanding when the facts are revealed, and feel very blessed for all of the support, especially from my friends and family."
Last year, Leaf had surgery to remove a benign tumor from his brain stem and later underwent additional radiation treatments.
On March 21, Leaf told an Associated Press reporter in an email exchange that he had struggled through treatments and had an MRI scheduled for the end of the month, but "I'm doing/feeling much better and am excited for the rest of 2012."
Farren said if the judge revokes Leaf's probation he could go to prison for longer than the probation term. The judge could treat each of Leaf's drug charges in Texas - seven counts of obtaining a controlled substance by fraud and one count of delivery of a simulated controlled substance - separately because that's the way the plea deals were done, he said.
Some of the charges carry sentence of up to 20 years in prison.
"The judge could stack them," Farren said.
In 2008, when Leaf was a quarterbacks coach for Division II West Texas A&M, he was accused of burglarizing a player's home. An investigation turned up that Leaf had obtained nearly 1,000 pain pills from area pharmacies in an eight-month span.
He resigned that year, was indicted in 2009. Besides the 10 years' probation, he was fined $20,000.
Last year, he wrote a book titled "596 Switch" - the name of a passing play in the Washington State playbook - that focused on the 1997 season when he led the Cougars to their first Rose Bowl in six decades.
Blaney reported from Lubbock, Texas.