HOUSTON — ­Now the Celtics and Rockets both know what it’s like to lose a late lead to the other.

After coming back from 26 down (12 behind in the fourth quarter) to beat the Rockets in the Garden in December, the Celtics were outscored 16-7 in the last three minutes last night to suffer a 123-120 loss, thus becoming Houston’s 15th straight victim. The C’s lost for the first time after four wins since All-Star break.

As the players had all said leading into the nationally televised affair, this wasn’t a playoff game. It did not, however, lack for playoff-type intensity — right down to a desperation fallaway trey from the left sideline by Marcus Smart that caught only iron at the buzzer.

“I just thought they maximized more possessions than we did,” said Celtics coach Brad Stevens. “But those were two good teams playing, and both teams deserve a lot of credit for how they played.”

Said Kyrie Irving, “I think just the flow of the game changed a little bit. They got some 50-50 basketballs. We understand they’re a 3-point shooting team. I just think some of the one-shot possessions we were hoping for we just didn’t get down the stretch that would probably have limited some of their second-chance opportunities, whether it be layups or another 3-point attempt.

“So down the stretch I think we did some good things. Obviously a few turnovers. A costly turnover on my end with a minute and some change left. But those plays of those long rebounds of them just getting it right back, it kept them in the game. We did a great job of running their shooters off the line, making them miss and we’ve just got to finish out certain possessions with a quality rebound. That was probably the difference in the game.”

Marcus Morris led the Celtics with 21 points, while Irving and Greg Monroe added 18 apiece and Terry Rozier had 17. Eric Gordon topped the Rockets with 29. James Harden had 26, but he went 6-for-18 from the floor.

The Celtics led, 113-107, after a Rozier 3-pointer with 4:01 left, but they came up dry on their next three trips up the floor.

PJ Tucker hit a 3, and James Harden scored on a drive. After Al Horford hit a jump hook over Harden with 2:04 left, the Celtics turned the ball over twice, as Trevor Ariza hit a trey and converted a Irving turnover into a fast break hoop.

The Celtics missed two more shots and turned the ball over yet again on their next two possessions, and Chris Paul’s two free throws gave Houston a 119-115 lead with 15 seconds to go.

Irving hit a layup, and Harden missed the second of two free throws with 7.4 seconds left to give the C’s a chance.

Irving was fouled at 5.2 before he could get off a trey. He made the first, but, though he appeared to try, couldn’t miss the second. It banked in.

“It’s really hard for Kyrie to miss, which is why he’s so special,” cracked Stevens.

Irving put it a different way.

“I suck at them,” he said. “I suck at them. I’ve been probably up there five, four times, and I’ve failed every single time at trying to miss on purpose. I don’t know. Don’t ask me. I keep telling my teammates, ‘I’m not good at missing.’ I’m not. I’m serious. (I) just think that I have to become better in order for our team to have a chance at the end of the game that I have to miss on purpose.”

Paul then made two more freebies, and Irving got fouled again with 2.8 seconds left. He made the first and missed the second on purpose. But he didn’t catch any of the rim, a violation.

Gordon made just the second of two from the line after being fouled at 2.3. With no timeouts left, the Celtics had to start in the backcourt, and Smart got his chance — albeit a very slim one.

“When I released it I thought it was (good),” Smart said. “I was looking to pass it. We ran a play for Kyrie or Terry to get those guys running down. But unfortunately the ball made a turn that we weren’t expecting and then, at the end, a lot of pressure on me falling out of bounds. That being said, I have to put it on the rim, make a play. It looked good to me, felt good. Part of the game.”

A frustrating part, in many senses. But the Celtics can’t be upset with the way they stayed in it against the team with the best record in the league.

“We turned the ball over a couple of times,” said Stevens of the way things went down the stretch. “We were wide open a couple of times, missed a couple of layups. Al was wide open on his. You take that 100 times out of 100. He had a great move down the paint. Smart was wide open on the jump shot. Kyrie had the layup that somehow didn’t go in. I have no idea. But I’ll take those shots all day long.”