Jalen Brunson made a go-ahead 3-pointer with 6.2 seconds left after the Knicks had blown a 21-point lead, and New York edged the Brooklyn Nets 124-122 on Friday night to improve to 2-0 in the NBA Cup.

Brunson missed a potential game-winning shot in a loss to Chicago on Wednesday but came through when the Knicks needed him this time and finished with 37 points. OG Anunoby added 25 and Mikal Bridges had 22 against his former team before partially blocking Dennis Schroder’s layup attempt on the final possession.

Cam Thomas scored a season-high 43 points for the Nets, his ninth career 40-point game and second at Madison Square Garden.

Playing without starting center Karl-Anthony Towns, who rested a bruised left knee, the Knicks led 98-77 with 30 seconds left in the third quarter before barely pulling out the opener of a weekend series between the teams. They meet again Sunday at Madison Square Garden — with the court back to its normal color after it was orange Friday for the tournament game.

Nets: With starting center Nic Claxton out at least a week with a lower back strain that required an epidural injection Friday, a Nets team already short on size is now even smaller. They were outrebounded 45-37 on Friday.

Knicks: New York missed a chance for a comfortable victory margin, which could come into play for tiebreaker purposes in the tournament.

Nets coach Jordi Fernandez challenged a call with 4:15 left on a ball that was ruled out of bounds off Dorian Finney-Smith. Referees reviewed the play and ruled that Anunoby had fouled Finney-Smith before the ball went out and called him for his sixth foul, knocking out one of the Knicks’ best players.

108-107. The Knicks regained the lead in the all-time series between city rivals.