-- BOSTON -- Due to their grueling December schedule so obviously conspiring against them in recent weeks, the Boston Celtics had every reason to roll over on Thursday night. The fresh-legged Houston Rockets had built a 26-point first-half lead, and Boston seemed to have no answer for containing James Harden and his teammates.
But on the second night of a back-to-back while playing shorthanded, the Celtics displayed some of the resiliency that decorated their 16-game winning streak earlier this season. Fueled almost entirely by energy on the defensive end -- and aided by two James Harden offensive fouls drawn by Marcus Smart in the final seconds -- the Celtics improbably rallied for a 99-98 triumph at TD Garden.
"The result doesn't matter. It's the resiliency that they showed," Celtics coach Brad Stevens said. "[The Celtics] could have easily folded."
It was Smart who reversed the momentum of the game with his defensive intensity. Then he stole the win by smothering Harden in the closing seconds.
Smart twice got Harden to commit offensive fouls over the final 7.3 seconds of play. The first gave the Celtics the ball down by one point, and Al Horford muscled home a floater from the baseline to put Boston out front for the first time all night.
Again, as Houston attempted to inbound, Smart stayed attached to Harden, who lowered his shoulder a bit and was whistled again as Smart went to the ground.
"First one, we were just trying to deny him the ball, and we were just trying to make it real uncomfortable for him the whole night," he said. "He lost it and gave me a little nudge, and it was kind of right in front of the official, and he called it. Then Al scores and he was getting ready to take the ball out, he's bumping me chest to chest. I'm just standing the spot getting ready to play defense again, so my hands are up and then, once again, he does the same thing.
"He loses it again, and the ref is right there again and called it. And that was pretty much the game."
Harden was 0-for-7 from the field with four turnovers when defended by Smart, according to tracking by ESPN Stats & Information.
After the game, Smart was asked if he got under Harden's skin.
"If that's what we want to call it, I probably did," he said.
Is that a role Smart is known for? "I guess you could say that," he said. "My mom might say that."
The Rockets were up by 20 points after one quarter, pushed their lead as high as 26, and led by 24 at the intermission. But Boston improbably responded with an energy-filled third quarter in which they outscored the Rockets 31-16 to pull within single digits heading to the final frame.
The Celtics seemed destined to look back and lament missed opportunities in the final three minutes. Boston couldn't convert multiple chances to tie or pull ahead late in the game.
But the Celtics never stopped fighting. Repeatedly down by three, Stevens and the Celtics elected to take 2-point baskets and try to force the Rockets into an error. It finally happened with 7.3 seconds to go when, after a Jayson Tatum dunk, Harden sent Smart to the floor trying to shake free to receive the inbounds pass.
After Horford's go-ahead basket, Harden got whistled again to the joy of a frenzied TD Garden.
"It just shows the value of Marcus Smart for our group, what he does to our team," Horford said. "It all started with him in the second half, in the third, picking up Harden, getting after him and just wearing him down. Staying after him. Smart's pretty banged up and he just kind of found a way to get [Harden] out of his comfort zone and play as hard as he could. That fueled the rest of our team."
In a game that featured a rare two-man referee crew, Harden did not attempt to hide his displeasure in the late-game calls.
"A lot of grabbing, a lot of holding," Harden said. "I mean, how else am I supposed to get open? Gotta ask with two arms wrapped around my whole body."
Harden led all scorers with 34 points, but on 7-of-27 shooting. Kyrie Irving finished with a team-high 26 points.
"I've had a few comebacks, but that was a special one," Irving said. "Just from how we started, it was so ugly man."
Horford, quiet for much of the night, was happy to produce the go-ahead bucket.
"Coach called a play. We were supposed to do some handoffs and the ball was eventually going to get into Kyrie's hands," Horford said. "[Coach] just looked at me and told me to take it. They guarded pretty well because everybody denied the guards, so it worked out perfect for me.
"I airballed the shot in the third quarter, that same shot earlier and missed another one. It's one of my go-to shots, so I felt like I was due to make one. It felt good."
The Rockets were shorthanded as well, playing without point guard Chris Paul, who missed his third straight game due to a left adductor strain suffered in a loss to the Los Angeles Lakers last week. Houston had lost its previous two games without Paul, continuing a theme in which the team struggled without the veteran point guard on the court this season. Before the loss to the Lakers, the Rockets had been 15-0 when Paul played this season.
Boston was without starting shooting guard Jaylen Brown, who missed his second consecutive game with right knee soreness, and rookie forward Semi Ojeleye, who missed his second straight game with back soreness.
Entering Thursday night, the Rockets were 179-0 over the past 20 seasons in games in which they led by at least 25 points. The Celtics previously overcame a deficit of more than 25 points on April 13, 2016, when they defeated the Miami Heat 98-88 despite a 26-point deficit.