Kanter will continue to survey the market until his Friday deadline, sources told ESPN, but barring an unforeseen significant change in the market, he will opt in.
Kanter had said in the weeks leading up to his decision that he had hoped to pursue a long-term deal this summer. In the current free-agent market, it would have been unlikely for Kanter to find a long-term contract that matched the annual value of his player option.
With Kanter on the roster for the 2018-19 season, the Knicks will have limited money to offer free agents this summer.
New York is currently projected to have an $8.6 million non-tax midlevel exception and a $3.4 million biannual exception to offer 2018 free agents.
Kanter will likely start at center for New York next season. He averaged 14 points and 11 rebounds in 71 starts for the Knicks, who finished the season 23-59.
Backup center Kyle O'Quinn declined his player option for next season. The club is open to offering a short-term deal to O'Quinn but prefers to maintain cap space for the summer of 2019, when players like Kyrie Irving and Kawhi Leonard may test the market.