Kemba Walker acknowledged it was "about time" he came up with his game-winning late efforts for the Boston Celtics against the Toronto Raptors.

The Celtics' major free-agent acquisition struggled in the team's opening loss to the Philadelphia 76ers on Wednesday, before continuing to have problems against defending champions the Raptors.

Walker had just 12 points at the Sixers, shooting 4-of-18 from the floor, including 1-of-8 from three-point range. He was a disappointing 4-of-13 and 1-of-5 against Toronto heading into the fourth quarter.

But the 29-year-old came off the bench with just over nine minutes of the game remaining and provided a spark for Boston, scoring 11 of the next 13 points for his team.

The Celtics ran out 112-106 winners, with Walker contributing 22 points and six rebounds in all.

"I was so happy," Walker said, via ESPN. "Like, 'About time'. It was a struggle, even from the last game to tonight.

"I wanted to be myself and these guys just allowed me to.

"I can't say enough about the people around me. The coaching staff, most importantly my team-mates, just really keeping me confident. They kept talking to me throughout the game.

"They knew I wanted to play well and I wanted to make shots, but I was struggling.

"But I can't say enough about it. They kept me confident. I really just appreciate those guys for keeping me level-headed, keeping me confident and just allowing me to be myself." 

Coach Brad Stevens was impressed, adding: "He just looked like he had an extra gear and he probably wasn't thinking about it going in. He was just going to be Kemba Walker."