Isaiah Hartenstein leaves Knicks, signs 3-year, $87 million deal with OKC Thunder

And then, it was just Mitch.

Despite owning home-court advantage in contract negotiations with free agent center Isaiah Hartenstein, the New York Knicks lost a key member to last season’s miraculous playoff run.

Hartenstein agreed to a three-year deal worth $87 million with the Oklahoma City Thunder, securing a massive payday after a two-year stint with the Knicks.

And he secured more than the Knicks could offer: New York owned Hartenstein’s Early Bird rights and could offer no more than a maximum of a 75 percent raise on his 2023-24 salary, or a four-year, $72.5 million deal.

The average annual value of the Knicks’ best offer came in at $18.1 million.

Hartenstein will earn an average of $29.16 million to join Shai Gilgeous-Alexander and Chet Holmgren on a title contender out West.

The Knicks are now down to just Mitchell Robinson and Jericho Sims as center options on a team they hope can compete with the Boston Celtics, Philadelphia 76ers and Milwaukee Bucks to represent the Eastern Conference in the NBA Finals.

Which could be a problem because Robinson is coming off of a season including not one, but two surgeries on a left foot that sustained a stress fracture in December.

In fact, Robinson’s injury is responsible for Hartenstein’s payday.

Hartenstein assumed the starting role shortly after Robinson left the rotation, and he thrived as a scorer, rebounder and play-maker, anchoring the paint for a Knicks team ultimately securing the Eastern Conference’s No. 2 seed.

He averaged 8.7 points, 9.4 rebounds, three assists, 1.3 steals and 1.3 blocks per game in the aftermath of Robinson’s Dec. 8 injury.

Only one player averaged as many steals and blocks over the course of the entire 2023-24 NBA season: Toronto Raptors franchise cornerstone Scottie Barnes.

In fact, only 12 players — Robinson, Hartenstein and Barnes included — averaged at least one steal and one block per game last season: Joel Embiid, Giannis Antetokounmpo, Anthony Davis, Jaren Jackson Jr., Victor Wembanyama, Derrick White, Jusuf Nurkic, Alex Caruso and Robert Williams III.

Hartenstein positioned himself as a premier player at the center spot last season with the Knicks.

Now, like many of his counterparts, he will be paid like one.

This loss is brutal for the Knicks, who believed Robinson and Hartenstein gave them the best one-two punch at the center spot in all of basketball.

The Knicks must now lean heavily on Robinson to shoulder the load at the five.

They have the $5.2 million tax-payer’s mid-level exception at their disposal to sign help at the center position.

The Knicks can also exceed the salary cap to re-sign Precious Achiuwa. However, they opted against tendering him a qualifying offer by his deadline, thus declining his status as a restricted free agent.

Achiuwa is free to sign with any team interested, but the Knicks can re-sign him with as much space as they have underneath the second apron, provided they create additional outgoing salary to satisfy the Mikal Bridges trade.

The Knicks can also use either the $6.8 million trade exception created in the Obi Toppin trade with the Indiana Pacers or the $5.2 million trade exception created in the RJ Barrett deal with the Toronto Raptors to acquire a player who is signed and traded by another team.

They have to do something, however, because Hartenstein’s departure leaves a gaping hole at the five and creates an immediate emergency in the event Robinson, who has played in just 31 games twice in the past four years, misses extended time due to injury.

The Knicks are rumored to have interest in Orlando Magic free agent center Goga Bitazde. They also drafted Ariel Hukporti with the 58th and final pick in the 2024 NBA Draft, and the seven-foot German-Togolese big man could be now be in play to make the trip to New York after initially being largely considered a draft-and-stash prospect.

Xavier Tillman could also be a prospect for the Knicks, and Tillman stepped up for the Boston Celtics in the NBA Finals after Kristaps Porzingis suffered a season-ending injury in the championship round.

Tillman, however, is a center who is only listed as 6-foot-7. The Knicks need the replace the size and skill they lost with Hartenstein’s departure. They could also take a flier on James Wiseman, the former No. 2 overall pick in the 2020 NBA Draft who hit unrestricted free agency this summer after a number of underwhelming seasons first with the Golden State Warriors, then most recently with the Detroit Pistons.

What’s clear is the Knicks need to do something.

The Celtics play five-out with Porzingis and Al Horford stretched beyond the three-point line most of the game. The 76ers have Embiid, who dominated the Knicks in the first round. The Indiana Pacers deploy Myles Turner, who is also an aggressive three-point threat, and then there’s the Milwaukee Bucks, who space the floor with Brook Lopez but could shake things up with Antetokounmpo at the five.

It won’t be easy given their salary cap constraints, but the Knicks have a strong roster they hope can compete for a title. Thea team’s only shortcoming now is depth at the five, which the front office will address to give the franchise its best chance at a championship since they made it to the NBA Finals in 1999.