Josh Hart and the New York Knicks have agreed to extend a midnight ET deadline on Saturday for his $12.9 million player option until Thursday, sources told ESPN.

Hart, a priority to retain on a new deal, could opt in and extend off that salary number for next season or decline the option and become an unrestricted free agent eligible to sign a new deal with the Knicks or another team.

An option for Hart that would deliver the Knicks cap flexibility would be an opt-in and extension off his $12.9 million for next season -- which he is eligible to do for up to 140% of that salary. This would give the Knicks access to using their full $12.4 million non-taxpayer midlevel exception. The Knicks have $149 million in guaranteed salary on the books for next season, which is $16 million below the luxury tax level.

Hart, 28, was a revelation after coming over from Portland in a deal at the NBA's trade deadline, reuniting with fellow former Villanova star Jalen Brunson.

Partnering with Immanuel Quickley to form one of the league's most potent second units, Hart shot a blistering 58% overall and 51.9% from 3-point range in 25 games as a Knick during the regular season. He was also a key part of New York's postseason run, fitting seamlessly into coach Tom Thibodeau's rotation.

Hart is one of the best undersized rebounders in the league and he's capable of defending multiple positions. He's also a good facilitator and finisher at the rim; the hot shooting he flashed in New York was the missing piece to complete an all-around offensive game.

The sixth-year pro has played on four teams across his NBA career, beginning with the Los Angeles Lakers before going to the New Orleans Pelicans for two-plus seasons and then spending a year -- across two seasons -- with Portland before being moved to New York.

ESPN's Tim Bontemps and Bobby Marks contributed to this report.