The New York Knicks are already taking lumps...and the 2015-16 NBA season hasn't even started.

The New York Post is reporting that Knicks coach Derek Fisher has been dating Matt Barnes's estranged wife, Gloria Govan, and the Memphis Grizzlies forward attacked Fisher when he found out.

Sources tell the Post that Barnes flipped out when he learned Fisher was in his former home on Saturday. Barnes was mad enough to leave Grizzlies training camp in Santa Barbara and drive 95 miles to Los Angeles to confront him.

"Derek was in Gloria’s back yard with about 10 people having a bonfire on ​​Saturday,” one source told the Post. "Derek’s separated from his wife and there’s a relationship with [Gloria]. [Barnes] went crazy."

Another source added: "Someone told Matt that Fisher was at the house and he drove down there — he went over to confront Derek."

A source close to Fisher said the Knicks' coach had a few scratches, but is "not going to press charges" and "he's going to let it go."

Fisher and Barnes were former teammates from 2010-12 with the Los Angeles Lakers.

In March, Fisher filed for divorce from his wife of 10 years, while Barnes and Govan have broken up, but are not officially divorced.

This report seems to be the reason why Fisher missed Knicks practice Monday with the team tweeting that he wasn't present due to personal reasons.

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(Photos from Left: Kevin Winter/Getty Images, Alex Goodlett/Getty Images)