The Boston Celtics crumbled to Ime Udoka’s Houston Rockets, tumbling twice defensively in the final 15 seconds of Monday night’s battle at TD Garden.

Houston executed back-to-back inbound plays, first catching Boston’s Luke Kornet off balance for a go-ahead dunk with 10.1 seconds left in the fourth quarter. Then again, on the next Rockets possession, Amen Thompson capitalized on a miscommunication between Kornet and Jaylen Brown and scored the game-deciding bucket.

The déjà vu effect came to life as the worst possible time for the C’s and although Kornet and Brown headlined the final defensive collapse, head coach Joe Mazzulla redirected all the blame to himself.

“Those last two plays were on me. Those are my fault,” Mazzulla told reporters after Boston’s 114-112 loss, per CLNS Media. “I didn’t put us in the best matchups. I saw the play that they were trying to run and I tried to change the matchups and I put our guys in a tough spot. That’s a tough one because I thought our guys did everything to win the game and they put us in position to win it and I didn’t help them at the end. So, both those plays 100% on me.”

Boston took a 12-point lead with 8:38 minutes remaining in the fourth quarter and made only four of their last 14 (28.6%) shots. But that was just the half of it. The Celtics also allowed the Rockets to muster up a 25-11 run to end the night and despite both untimely setbacks, the reigning champions had a chance to escape victorious.

Jayson Tatum cleaned up Boston’s first defensive miscue with a game-tying layup, shaking off a scoreless first half to come through in the biggest moment. Yet, as Mazzulla pinpointed, those efforts were squandered. Tatum’s clutch basket went to waste once Udoka’s squad pulled the carpet out from underneath Boston’s defense, leaving everyone at TD Garden gasping in disbelief.

The defeat marked Boston’s ninth this season in which the team has blown a fourth-quarter lead, matching last season’s total through 82 games.

“It kind of just was within the timing of all of it,” Kornet told reporters, as seen on NBC Sports Boston’s postgame coverage. “Obviously we were trying to switch. It was a weird thing of kind of like the ball was being handed in and stuff and then kind of second-guessing it at the same time because we were trying to get in position. So yeah, it just didn’t play out in a good way and it’s kind of hard to say exactly — with just the timing of it and trying to make it happen and I think it was a good move to try and get that going but it played out in an unfortunate way.”

Just when it seems as though the Celtics are about to put together their first major which Brown claimed would come, the team topples over like a Jenga tower. Boston has gone 3-9 in games following a win since Dec. 18, including 4-6 at home amid that stretch, and they haven’t won three or more times consecutively since Dec. 31 through Jan. 3.

Does that warrant a panic button smash? Not really. Does it warrant some serious film sessions and urgent readjustments? Absolutely.

Post-championship hangovers are the norm as the Golden State Warriors were the last team to go back-to-back — seven years ago — but cold streaks should end. The Celtics haven’t performed like themselves last season and while they remain possessors of the NBA’s third-best record at 32-15, legitimate flaws have been presented and exploited.

With 35 games left in the regular season including an All-Star break intermission, Boston has time on its side.