Ben Simmons put his one-point showing in the 76ers' Game 2 loss to the Celtics on one thing: "I was thinking too much".

Simmons failed to score a field goal for the first time in his career as the 76ers suffered an 108-103 defeat at TD Garden on Thursday to go 2-0 down in the second round of the NBA playoffs.

The Australian forward believes it would have been a different story if he had let his natural instincts take over.

"I think it was mainly what I did to myself. Mentally, I was thinking too much, overthinking the plays. Wasn't just out there, flowing, playing the way that I play, which is free," said the 21-year-old.

"I think, obviously, [the Celtics] have a game plan, I know what their game plan is and I've got to play my game."

The Rookie of the Year contender added: "I think the way the Heat played [against Simmons in the first round], it was nothing compared to the Celtics. Physically, the Heat were on another level.

"I'm going to have bad games; it happens. Obviously, it's not the perfect timing. But we're headed home now.

"We're learning, we're a young team. Nobody is panicking in the locker room, nobody's freaking out. We're staying together as a team. We go home and we've got to take care of business."