The point guard departed in the second quarter with soreness in his left knee and did not return, as his team went on to claim a 109-102 win at Barclays Center.
Simmons, who was traded to the Nets from the Philadelphia 76ers in February this year, has already missed six games this term with the same problem.
Nets coach Jacque Vaughn revealed it was the 26-year-old's request to exit the match, but believes there is nothing too serious to be concerned about with his injury.
"We'll check him day by day, see how he responds with a little treatment," he said. "[We will] see what it looks like [on Tuesday]."
"I think more so than anything, [it is] the accumulation of games. He hasn't had this amount of accumulation of games over a period [for] a long time.
"[We] talked to the performance team about that. We were warned about that just as these games [started] to add up.
"It's really stretching him sometimes. The amount of games we've just had, with the minutes that he's played, [have been] pretty high going into tonight's game."
Simmons' absence is a blow for the Nets, with the Australian having arguably found his best form of the campaign this month, with an average of 10.5 points, 7.0 rebounds and 5.2 assists across November.