The New York Yankees do not intend to pay Jacoby Ellsbury the remaining $26 million due under his contract, contending he violated the deal by receiving unauthorized medical treatment, sources confirmed to ESPN's Buster Olney on Friday.

According to multiple reports, Yankees general manager Brian Cashman sent a letter to Ellsbury and his agent, Scott Boras, informing them that the team had converted his contract to a nonguaranteed deal.

The Yankees said that Ellsbury, who has not played since 2017 because of myriad injuries, was treated by Dr. Viktor Bouquette of Progressive Medical Center in Atlanta without the team's permission, according to multiple reports.

The New York Post first reported that the Yankees didn't intend to pay Ellsbury, who had two years remaining on his seven-year, $153 million contract when he was released Wednesday.

Ellsbury and the Major League Baseball Players Association can file a grievance challenging the conversion of the contract to nonguaranteed.

"The players' association will vigorously defend any action taken against Jacoby or his contract and is investigating potential contract violations by his employer," the union said in a statement.

Ellsbury is owed $26,285,714 by the Yankees in one of their biggest free-agent mistakes: $21,142,857 for next season plus a $5 million buyout of a $21 million team option for 2021. If Ellsbury is not paid, that amount would come off the Yankees' luxury-tax payroll next year.

He was released Wednesday to clear a 40-man roster spot as the Yankees added seven players to protect them from next month's Rule 5 draft.

Now 36, Ellsbury hit .264 with 39 homers, 198 RBIs and 102 stolen bases in 520 games over four seasons with the Yankees. He spent his first seven seasons with the Boston Red Sox and was an All-Star in 2011, and he arrived in New York after compiling a .297 career average, 65 homers, 314 RBIs and 241 steals for Boston.

Ellsbury injured an oblique muscle on his right side early during spring training in 2018, developed a bad back and had hip surgery on Aug. 6 last year to repair a torn labrum in his left hip. He experienced plantar fasciitis in his right foot during his rehab program before spring training this year.

The Associated Press contributed to this report.