Boston (6-6) led the NBA in defensive field-goal percentage last season at 41.9, but that type of defense is a distant memory now. The Celtics rank 27th in that department in 2012-13 at 46.3 percent, allowing San Antonio to shoot 58.4 percent in Wednesday's 112-100 loss.
The Celtics allowed an opponent to score over 100 points for the second straight game, including a 103-83 defeat to lowly Detroit on Sunday.
"We just have to learn, continue to learn and build," forward Paul Pierce said. "We've given up 100 points the last couple of games. That's definitely not our identity."
Now the Celtics will face Durant, who is second in the NBA with 25.4 points per game and put up a pair of 28-point efforts last season to help Oklahoma City (9-3) sweep Boston.
The Thunder superstar is heating up with a season-high 35-point performance in Wednesday's 117-111 overtime win over the Clippers. He had a league season-best 21 free-throw attempts.
"I think early on, me driving and me getting into the paint, I was a little hesitant in the second half because I was turning the ball over," Durant said. "But I just tried to keep going. My teammates told me to just keep being aggressive, and that's what I tried to do."
Coach Scott Brooks was happy that his team limited Los Angeles to 45.6 percent shooting. The Thunder are fifth in the league in that category at 42.8.
"That's what we talk about every game, keeping it in the low 40s and we did that tonight," Brooks said.
Thabeet, a bust since being the No. 2 overall pick by Memphis in 2009, had 10 points and four boards Wednesday.
"I think Hasheem is the player of the game just the way he plays," Durant said. "His energy, in that second unit, his intensity, rolling to the basket he causes so much attention."
Boston's Rajon Rondo had 22 points and 15 assists Wednesday, but could not contain Spurs point guard Tony Parker (26 points).
"The best thing about the league is you don't have to wait a week to play another game," said Rondo, who leads the NBA with 13.3 assists per game. "After Thanksgiving, we'll get back and try to get focused with Oklahoma City."
Rondo has gone 35 straight games with at least 10 assists and faces another tough point guard matchup against Russell Westbrook, who had 23 points and nine assists Wednesday when he was facing Chris Paul.
Westbrook averaged 28.5 points against the Celtics last season, with Rondo missing one of the games due to suspension.