Amid anticipation that he would make his season debut on Monday, Ben Simmons has been ruled out for Game 4 of the Brooklyn Nets' first-round playoff series against the Boston Celtics.

Multiple reports last week stated the Nets intended for Simmons to play on Monday if his recovery from a lingering back injury and lengthy layoff from basketball remained on course. "Return to competition reconditioning/back soreness" was the official reason listed by the Nets on Sunday for Simmons' continued absence.

ESPN's Adrian Wojnarowski reported Simmons woke up with back soreness on Sunday after participating in basketball activities on Saturday and that he and the Nets collectively decided he would remain sidelined on Monday.

Simmons hasn't played an NBA game since the Philadelphia 76ers were eliminated in the second round of last season's playoffs by the Atlanta Hawks. The Nets traded for Simmons midseason in a package that sent James Harden to the 76ers, anticipating Simmons could contribute to a playoff run alongside fellow All-Stars Kevin Durant and Kyrie Irving. He has yet to make his Nets debut.

The Nets lost to the Celtics on Saturday in a series Boston now leads 3-0, putting Brooklyn at historically long odds to remain alive in its quest for an NBA championship. No NBA team has ever rallied from a 3-0 deficit to win a playoff series.

Brooklyn's decision to trade a disgruntled Harden for Simmons was a gamble dependent on Simmons' availability to pay off. The Nets started the season as favorites to win the NBA championship, only to see their regular season derailed by chemistry issues, a lingering Durant knee injury and Irving's limited availability due to his COVID-19 vaccination status. Now they're on the brink of first-round playoff elimination while facing a strong likelihood that Simmons doesn't play a game this season.