Mitchell Robinson, already out for the playoffs, underwent a “small procedure” on his left ankle Monday and will be re-evaluated in 6-8 weeks, a league source told The Post.

It was the second surgery to Robinson’s ankle, which was diagnosed with a stress fracture in December.

The Knicks center returned in late March but suffered a setback in the playoffs and was pulled after the first half of Game 1 in the Eastern Conference semis.

Robinson was said to have suffered a “stress reaction” in his surgically repaired ankle.

However, at the time, another surgery was not advised.

A source said further consultation between Robinson’s surgeon and Knicks doctors determined the second procedure was “the best course of action.”

It became the latest turn in Robinson’s recovery.

Not long after his initial surgery, the Knicks applied for the Disabled Players Exception for Robinson – suggesting his season was over.

But the DPE application was denied and Robinson, an All-Defense candidate until the injury, came back with just 11 games remaining in the regular season.

He was then a backup to Isaiah Hartenstein and an integral part of beating the Sixers in Round 1, handling much of the defensive duties on Joel Embiid. But Robinson was re-injured during those battles with Embiid.

After Game 3 against the Sixers, he left the arena in a walking boot and missed the following contest.

He returned again but was hobbling through his minutes.

After this season, Robinson has two years and roughly $27 million remaining on his contract.

Hartenstein and another Knicks center, Precious Achiuwa, are free agents this summer.