NEW YORK — Ben Simmons is on the brink of returning but it won’t matter if his teammates don’t handle business in Game 3. Simmons’ recovery plan includes one more pain-free workout Saturday before he’s cleared from his back injury, leaving Monday’s Game 4 as a strong possibility for the 25-year-old’s Nets debut. However, the Nets also need to win Saturday to avoid going down 3-0 to the Celtics, a deficit never conquered in the NBA. Simmons’ impending return, in other words, adds another wrinkle and even higher stakes to Game 3 at Barclays Center, where Kevin Durant and Kyrie Irving will attemp…