Irving and Embiid struggled early, going a combined one for 10 from the field in the first quarter. Despite ending the quarter pointless, Embiid was able to make an impact on defense, notably swatting away Irving's attempted layup.
Embiid and Simmons helped out Redick at the start of the second and the 76ers made their first nine shots of the quarter to open the 22-point lead with 6:56 remaining in the quarter.
However, Irving finally made a three-pointer, sparking a strong Celtics finish to the half as they closed to 57-48.
Having been outshone by fellow rookie-of-the-year contender Simmons in the first half, Tatum began the second half hot, making his first five shots to bring the Celtics within a point.
The Celtics soon took their first lead midway through the third quarter.
at Toronto 133, Cleveland 99:
After losing to Minnesota 127-99 on Monday, the Cavaliers fell by an even bigger margin. Toronto's 133 points were the most by any Cavaliers opponent this season, and marked the third straight game that Cleveland has allowed at least 127.
Fred VanVleet scored a career-high 22 points,
C.J.Miles scored 16 points, Pascal Siakam and Norm Powell each had 14 and
VanVleet made six of eight 3-point attempts as the Raptors connected on a season-high 18 shots from beyond the arc.
9 p.m.: This articles has been updated with results of the Cavaliers-Raptors game.