The Athletic's Shams Charania reports Irving will be inactive for Game 5 due to a right ankle sprain experienced in a 107-96 loss at Milwaukee, which tied the series at 2-2, on Sunday (June 13.)
The All-Star guard appeared to grab his ankle after the fall and missed the remainder of the game.
Nets coach Steve Nash said x-rays on Irving's ankle were negative, but the team planned to further evaluate and treat the injury before making a decision on the guard's status for Game 5 prior to Charania's report.
Irving is currently averaging 20.0 points, 4.3 assists and 5.0 rebounds in the Nets' Eastern Conference semifinals series against the Bucks.
The former NBA Champion was the only Nets player other than Kevin Durant -- who scored a team-best 28 points -- to finish Game 4 in double figures for scoring.
The Nets are already without fellow All-Star guard James Harden, who experienced a hamstring injury in the opening minute of Game 1.
Veteran forward Jeff Green returned from injury in Game 4 and recorded eight points, five rebounds and one assists in 27 minutes of action on Sunday.