The Celtics swept the best-of-seven Eastern Conference first-round series four games to none — the first sweep in 15 playoff series between the East rivals.
For Walker, who arrived in Boston after eight seasons of frustration with the Charlotte Hornets, it was a first NBA playoff series win.
With their backs against the wall, Joel Embiid and the 76ers kept it close and trailed by just two points late in the third quarter before forward Tobias Harris took a hard fall under the basket, his head slamming the hardwood.
Harris was able to leave the court under his own steam, holding a towel to his left eye and temple, and returned after treatment for what the team called a laceration over his left eye.
But the Celtics closed the third quarter on a 12-0 run that effectively spelled the end of the 76ers’ hopes.
Embiid, desperate to avoid being swept, finished with 30 points, 10 rebounds and five assists for Philadelphia.
Harris scored 20 as six 76ers players scored in double figures — but it was the Celtics who advanced to a second-round clash with either the defending champion Toronto Raptors or Brooklyn.
The Raptors took a 3-0 series lead into their game against the Nets later Sunday.