Free agent center Isaiah Hartenstein has agreed to a three-year, $87 million deal with the Oklahoma City Thunder, sources told ESPN. He leaves the New York Knicks for the top West seed eager to add his size, skill and physicality.

Hartenstein, 26, established himself as a quality starting center this past season for the Knicks, stepping into that role for New York after Mitchell Robinson suffered an ankle injury in December.

Hartenstein became a key part of a magical season for the Knicks, who won 50 games as well as a playoff series for a second straight season for the first time since 2000. He averaged 7.8 points and 8.3 rebounds, playing in 75 games (49 starts) while shooting 64.4% from the field.

Hartenstein was one of just three players last season with at least 85 blocks and 85 steals, and he held opponents to shooting below 53% at the rim. Along with elite defense, Hartenstein possesses impressive vision and playmaking ability for a center, although that aspect of his game didn't feature prominently in Tom Thibodeau's offensive system.

Hartenstein opened his career playing two seasons for the Houston Rockets before bouncing around to the Denver Nuggets, Cleveland Cavaliers and LA Clippers ahead of signing a two-year deal with New York in the summer of 2022.

Because the Knicks have only early Bird rights on Hartenstein, the most New York could offer him was four years, $72.5 million.

The Thunder also agreed to long-term extensions with key reserves Isaiah Joe and Aaron Wiggins, league sources confirmed to ESPN.

Sources said that Wiggins agreed to a five-year, $47 million contract and Joe agreed to a four-year, $48 million deal.

The Thunder declined relatively small team options on Joe ($2.1 million) and Wiggins ($2 million) with the intention of securing them to multiyear deals.

ESPN Stats & Information, Tim Bontemps and Tim MacMahon contributed to this report.