Allen, Nets can’t agree on contract extension

Center Jarrett Allen won’t just be playing for a championship. He’ll be playing for a contract, too, after he and the Nets didn’t agree on an extension before Monday’s deadline.

That means the 22-yearold Allen, long considered a cornerstone for Brooklyn, is going to be a restricted free agent after this season presuming the Nets tender him a qualifying offer of $5.7 million. Or don’t trade him first.

The news was confirmed by The Post, and was first reported by Yahoo.

Allen averaged 15.7 points, 11 rebounds and a surprising 4.2 assists in six seeding games in the NBA bubble this summer, and 10.3 points and 14.8 rebounds in the first-round playoff loss to Toronto.

The young center comes into Tuesday’s season opener against Golden State having already racked up 20.0 win shares, the most of any player in the 2017 draft class, according to Basketball-Reference. More than Bam Adebayo, Jayson Tatum, Donovan Mitchell and De’Aaron Fox, all of whom landed five-year $163 million max extensions.

OG Anunoby, Markelle Fultz, Jonathan Isaac, Luke Kennard and Derrick

White all got extensions on Monday. And even closer to home, the Nets had handed rookie extensions to both Caris LeVert and Taurean Prince last year.

Last month, former Nets assistant GM Bobby Marks — now ESPN’s cap guru — had reported that Allen was looking for “Clint Capela money.” That’s in the range of five years and $90 million.

Marks felt that Allen’s body of work could get him $14-$16 million, either from the Nets or another team on an offer sheet.

Now Allen will go into the restricted free agent pool next summer among the best big men, behind Andre Drummond and John Collins. Currently a bargain at $3.9 million, Allen has been linked in trade rumors for Houston’s James Harden, and could find himself moved before the deadline.

The Nets’ payroll has swelled to $140 million and owner Joe Tsai is facing a hefty luxury-tax bill.

➤ The Nets exercised fourth-year team option on Landry Shamet.

➤ Nic Claxton (knee tendinopathy) and Golden State’s Draymond Green are both out Tuesday.