The point guard missed four games due to a knee problem but was back in action at American Airlines Center.
Simmons was on court for just under 16 minutes after coming off the bench, scoring two points, claiming three rebounds and providing two assists in a 96-94 loss.
The Australia star gave a frank assessment of his performance in Dallas, where the Nets slipped to 4-7.
"I'm my harshest critic, so I think terrible," Simmons said. "There's a place I want to get to. I got to keep working, I got to keep pushing myself and adapting, so I'll get there."
Simmons said coming through his comeback pain-free was the primary objective
"That was the main thing for me," Simmons said. "Just have no pain. Get up and down the floor, sprint, run, jump, so I felt good."
Nets interim coach Jacque Vaughn welcomed the opportunity to have Simmons involved again.
"Great to see him out on the floor," Vaughn said. "I put him out there with a group that could play fast, hoping to get some shooters around him.
"At that stretch, we didn't make a lot of shots. But, overall, seeing him back on the floor, he played with speed, he played with pace, which is good."