Isaiah Hartenstein bolts Knicks for $87 million Thunder contract in NBA free agency

The Thunder made Isaiah Hartenstein an offer he couldn’t refuse and one the Knicks couldn’t match.

Hartenstein, the beloved Knicks center, has agreed to a three-year, $87 million contract with the No. 1 seed in the Western Conference this past season, according to ESPN.

The Knicks could only offer four years and $72.5 million.

Hartenstein’s representatives worked on the deal overnight as the NBA free agency window opened Sunday, per ESPN, and the Thunder added much-needed size.

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The Knicks will now have to find a backup center in what is a limited market.

Hartenstein’s contract features an annual average value of $29 million, which is more than 50 percent greater than the $18.1 million his Knicks deal would have featured.