Unfortunately for the Celtics, there was still a dominant point guard on the floor.
Rookie Kyrie Irving capped his latest impressive effort - and the Cavaliers' game-ending 12-0 run - with a last-second layup that ended Boston's four-game winning streak, a loss the Celtics will try to avenge Tuesday night in Cleveland.
Boston moved back to .500 with four straight victories after a 5-9 start, and the Celtics looked well on their way to a fifth when Brandon Bass' free throw put them up 87-76 on the Cavaliers with 4:25 left Sunday.
That was the last point Boston (9-10) would score. Irving had six of his game-high 23 points in the final 4:13, splitting two defenders for a layup with 2.6 seconds left to give Cleveland a stunning 88-87 victory.
"I thought he dominated the fourth quarter," Celtics coach Doc Rivers said. "He single-handedly, in my opinion, willed that win for them."
It was the same play the Cavaliers (8-11) called for Irving with the score tied in the waning seconds Dec. 30 at Indiana. He missed an easy runner in that spot, and the Pacers went on to win in overtime.
"He (learned) not to miss the layup this time," Cleveland coach Byron Scott said. "He had that little look in his eye like he wanted it, almost like he wanted to redeem himself."
Irving, who had a season-high 32 points Friday in a home loss to New Jersey and leads all rookies with 17.9 per game, isn't just putting up points. He's also been remarkably efficient with his attempts, shooting 51.6 percent to rank fifth in the league among guards - just behind Allen and Rondo.
Though the Duke product isn't even one-third of the way through his first season, he's holding some impressive company early. No rookie guard has shot a higher percentage over a full season since Magic Johnson connected on 53.0 percent in 1979-80.
Irving made 10 of 14 shots Sunday. His clutch play late made the defeat difficult to swallow for Boston, which held its opponents to 36.9 percent shooting during the winning streak before the Cavaliers shot 43.0 percent.
"This was a bad loss for us," Rivers said. "Not that it was Cleveland; it was that we had the game under control. And we didn't take care of it."
Rondo won't play again Tuesday - he could return later this week - but Allen looked good Sunday after sitting for three games with an injured ankle. The 10-time All-Star had 22 points on 9-of-14 shooting in his first game back, a vast improvement over the 9.3 points he averaged while shooting 40.4 percent in his previous seven contests.
Rondo's absence has forced the Celtics to run their offense through Paul Pierce more often, and while Pierce has averaged 24.6 points and 8.0 assists in his last five games, he's also averaged 5.2 turnovers.
He gave it away seven times against the Cavaliers, his most in nearly two years.
Boston also needs to figure out a way to slow Anderson Varejao, who had 18 points and nine boards Sunday. He's averaged 14.6 points and 10.2 rebounds in his last five regular-season games against the Celtics while shooting 69.8 percent.
Boston returns to TD Garden for a five-game homestand starting Wednesday, but it's eager to have another shot at the Cavaliers so soon.
"We'll be prepared," guard Avery Bradley said. "We just need to come with a chip on our shoulders and come and play hard like we've been doing."