Ben Simmons smiled and chuckled about the way he had been acting all day. Wednesday was the first time in 16 months that he had played in a meaningful basketball game, and he seemed positively effervescent.

“I think I was just too excited, honestly,” he said Wednesday night at Barclays Center. “It was just great to be out there.”

The outing did not go especially well. Simmons scored only 4 points and fouled out, perhaps a function of his enthusiasm, and his team lost, 130-108, to the New Orleans Pelicans in the N.B.A. season opener for both teams. He was a bit rusty having missed all of last season with mental and physical health problems, starting in Philadelphia before he was traded to Brooklyn. But just the fact that Simmons played in the game was momentous.

His availability is emblematic of where the Nets find themselves at the start of this season. Kevin Durant is still on the team. Kyrie Irving should be available all season. And now Simmons is healthy. This season could offer a final word on what the Durant-Irving Nets can be, and how they respond to the pressure of having the pieces in place to be real contenders.