The Celtics offered no excuses after their deplorable 117-106 loss to the struggling New York Knicks on Wednesday at TD Garden. Maybe that’s the first sign of progress.

The players stood up and admitted they had been outplayed, outhustled and outdesired. The Knicks were desperate, with the Phil Jackson-Carmelo Anthony soap opera hovering over their decaying franchise. The Celtics should have expected desperation, but they did little to offset New York’s passion.

They allow a rookie named Mindaugas Kuzminskas to score 9 points in the opening quarter. They allowed a rookie named Willy Hernangomez to scored 17 points with 11 rebounds in 19 minutes. Meanwhile, the Celtics tried to rely solely on Isaiah Thomas and even he lacked the heroics for another fourth-quarter rally.

The Celtics ran out of answers in the final period, and their weaknesses were exposed. They were pounded on the boards (57-33) and their defense allowed a team that had shot 50 percent once in the past 36 games to well, shoot 50.5 percent.

Boston’s defense has been abysmal of late, only compensated for by stellar offense and the incredible play of Thomas. But to go far in the playoffs, to become an Eastern Conference contender, the Celtics are going to have to stop somebody.

Derrick Rose looked vintage Rose on Wednesday. He made 13 of 24 shots and seven of his makes were layups. As acrobatic and impressive as those layups were, Rose was still allowed to attack the rim at will. And when he didn’t, he simply peppered the Celtics with mid-range jump shots.

Anthony scored just 13 points on 14 shots. He never imposed his will on the game and he didn’t need to. The New York bench scored 55 points with 35 rebounds. The Celtics bench scored 27 points with 8 rebounds.

“Nope,’’ was Jae Crowder’s response when asked if the Celtics were due for a clunker. “We just got outplayed from start to finish. They wanted it more than we did and it showed. They had lost a lot of games in a row and we should have known they were going to come out with a little fire but we never matched it. We just played from behind.’’

These things happen in the NBA. Houston lost at Miami. Cleveland lost to Portland. Toronto lost to Philadelphia. San Antonio lost at home to Milwaukee with Giannis Antetokounmpo playing nine minutes. Good teams are due for wake-up calls, but the question is whether the Celtics really consider this a wake-up call and decide to address their issues.

The Celtics are 28th in the NBA in rebounding with 41 per game (the Knicks are third, so this slaughter may have been expected) but they have to offer more resistance. Rose and Hernangomez outrebounded Al Horford and Amir Johnson, 21-14.

The Celtics are 22nd in the NBA in defensive rating this month and 15th in opponent’s field goal percentage. They are getting by on offense, and Thomas, more specifically. On Wednesday there were several occasions where they could have turned the game around with defensive stops and they were incapable.

“We talked about the defensive stuff,’’ Celtics coach Brad Stevens said. “We’ve got to defend a lot better, we know that. But all the technical stuff is out the window if you’re not flying around. And we weren’t flying around.’’

This loss could serve as a positive benchmark if the Celtics react accordingly. They have been slipping of late, besides Thomas. And he showed vulnerability on Wednesday. While he scored 20 second-half points, he was 4-for-15 shooting and attempted eight 3-pointers. On several occasions against the Knicks, he launched long-range shots hoping they would go in, because they usually do. But they won’t all the time.

It wasn’t that the Celtics have been lured into thinking Thomas will save them every time, but he needs more help. The trio of Horford, Marcus Smart, and Terry Rozier were a combined 4-for-28 shooting. Horford and Smart, who started in the place of the injured Avery Bradley, scored 2 points apiece in the second half in 32 combined minutes. That’s not on Thomas.

It was one of those bizarre nights where the Celtics missed shots they usually make. But 106 points should be good enough to win games against most teams, especially the Knicks in their current state. It wasn’t enough Wednesday because those weaknesses that have been camouflaged by Thomas’s greatness surfaced because he wasn’t great Wednesday.

So the Celtics have some work to do. They are not Toronto. They are not Cleveland. They can’t overlook opponents, but getting sucker-punched every now and then in the NBA happens. The appropriate reaction is to improve on those issues that need to be addressed. The defense has to become a strength. The rebounds have to increase. Opposing players are disrespecting the Celtics on the offensive boards, merely reaching over the out-of-position player and scoring at will. New York grabbed 18 offensive rebounds, which is unacceptable.

So at the midway point in the season, it’s time for the Celtics to reassess and make positive strides towards being elite. They are capable, but improving — not relying on Isaiah Thomas — has to be a point of emphasis or more sucker punches are on the horizon.

Gary Washburn can be reached at gwashburn@globe.com. Follow him on Twitter @GwashburnGlobe.