BOSTON – The 76ers have to be happy that Monday's game didn't count.

They couldn't defend or make outside shots in a 113-96 setback to the Boston Celtics at TD Garden. The mismatch was basically over midway through the first quarter with the Celtics up, 17-5.

"We will watch film and try to figure it out," said Jahlil Okafor, who started at center. "But they were tougher than we were. This was bad. This was bad for all of us."

Ben Simmons paced the Sixers (0-3) with 15 points. The point guard also had six rebounds, two assists, two blocks and a steal. However, he made just 3 of 10 foul shots and still needs to improve on the defensive end.

Furkan Korkmaz added 13 points and six rebounds. Markelle Fultz had 12 points off the bench after sitting out Friday's home loss to Boston with a sore right shoulder. The first overall pick attacked the rim, but made just 2 of 4 foul shots. A three-point threat in college, Fultz did not attempt a three.

Dario Saric finished with nine points and seven rebounds in his first game of the season. The power forward sat out the first two games to rest.

Semi Ojeleye paced the Celtics (3-0) with 16 points.

This game was a homecoming for Sixers reserve Amir Johnson (four points). The post player played the last two seasons for the Celtics.

"It's good to be back in Boston," Johnson said Monday morning, "My family's out here. My son [A.J.] was born here [in June.]"

The Johnsons made the trip to Beantown to get the birth certificate for Amir's son A.J., who was born on June. 3. Unfortunately for them, everything was closed because Monday was Columbus Day.

J.J. Redick, the Sixers' other offseason free-agent acquisition, and Robert Covington had the night off to rest. The Celtics did the same thing with Kyrie Irving, Gordon Hayward, Al Horford and North Philly's Marcus Morris.

In addition to Fultz and Saric, Timothe Luwawu-Cabarrot (right knee patellar tendinitis) returned to action. The second-year guard had seven points.

The Sixers made just 28 percent on their three-pointers. The Celtics made 41.4 percent of their threes