The Durst Organization jumped through hoops to revitalize 1133 Sixth Ave. with $40 million in capital upgrades after the IRS moved out in 2014 and left the address 30 percent vacant.

Now, a professional basketball union has come through at the buzzer to fill the 1.1 million-square-foot tower’s last available space.

The National Basketball Players Association, which represents current NBA players, signed a lease for just under 9,000 square feet — bringing its total to 56,187 square feet.

The NBPA’s space in the building includes a regulation-size basketball court.