Even with ample warning, the New York Knicks couldn’t prevent the inevitable.

Isaiah Hartenstein is unofficially headed to Oklahoma City, where he’ll compete for a championship with the Western Conference’s top-seeded team, leaving the Knicks in search of a replacement.

Hartenstein agreed to a three-year, $87 million deal with the Oklahoma City Thunder on Monday, according to The Athletic’s Shams Charania. The Knicks, who signed Hartenstein to a modest contract a couple of summers ago, anticipated losing their starting center.

Due to a unique aspect of the collective bargaining agreement, the Knicks were limited in how much they could offer Hartenstein. Their maximum offer was $72.5 million over four years, with only $64 million guaranteed. After the NBA Finals concluded and free agency negotiations began, the Knicks made their best offer to Hartenstein, according to a league source. However, the 26-year-old chose to explore free agency, expecting better offers.

He was right.

Before free agency started, Hartenstein’s representatives informed the Knicks that they should anticipate other teams making more lucrative offers, according to league sources. Hartenstein, who had expressed a desire to return to the Knicks, said that if all things were equal, he would have stayed with the team that helped him break out.

Hartenstein had signed a two-year, $18 million contract with the Knicks just a couple of summers ago and had since developed into Jalen Brunson’s go-to pick-and-roll partner, a defensive powerhouse, and a favorite of analytics experts. Despite the Knicks’ strong desire to keep him, and Hartenstein’s consideration of returning, the financial disparity was too significant.

The Knicks never withdrew their offer to Hartenstein, even as they prepared for his departure, according to a league source.

Barring a major trade, the Knicks already have next season’s starting center: Mitchell Robinson.

No remaining free-agent center matches Hartenstein’s skill set. The available options include Goga Bitadze, Moe Wagner, Daniel Theis, Thomas Bryant, and Mo Bamba. Other 2024 free agents, such as Nicolas Claxton, Jonas Valančiūnas, Andre Drummond, Drew Eubanks, Kevin Love, Mason Plumlee, and Luke Kornet, have already signed with other teams.

One player to keep an eye on is Precious Achiuwa, the unrestricted free agent who impressed as a backup center and power forward for the Knicks last season.