By Matthew Geagan, CBS Boston

BOSTON (CBS) — Kemba Walker usually thrives with the ball in his hand and a chance to win the game. But on Saturday night, nothing wanted to fall for the point guard, and it cost the Celtics in the team’s biggest game of the season.

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Walker had a step-back attempt to win it in the final frantic seconds against the Los Angeles Lakers, a shot that he’s made a career of sinking. While most fans would prefer it if Jayson Tatum and Jaylen Brown were putting up Boston’s game-winning attempt, Walker is a solid third option. At least, the usual version of Kemba Walker is a fine fit for that role.

The current version of Walker, however, is not the Cardiac Kemba that basketball fans know. He caused heart palpitations for all the wrong reasons against L.A., finishing with just four points off 1-for-12 shooting from the floor. Despite those struggles throughout the game, a 2-for-12 shooting line would have won it for Boston.

But Walker’s final look from 13-feet out clanged off the back rim, Daniel Theis wasn’t able to finish a put-back attempt, and the Celtics fell in crushing fashion to their historic rival, 96-95. Boston is now 10-8 on the season.

“I thought I had a good look, but I struggled all game shooting the basketball,” Walker said after the loss. “I would have loved to make some shots tonight. It was a struggle obviously. I would have loved to help my teammates more tonight, but it didn’t go that way. I have to keep working, just find myself a little bit, find my rhythm, find my spots.”

Walker was able to generate a handful of clean looks against the Lakers, they just didn’t fall from anywhere on the court. He missed all five of his threes and all four of his looks from inside the paint. Walker is still lacking his patented craftiness under the hoop, with Montrezl Harrell rejecting a pair of close-range attempts on Saturday.

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After missing the first 12 games of the season to strengthen his knee, Walker is still working to return to form. Some rustiness was to be expected, but he’s said that he feels great since his return. After Saturday’s loss, the 30-year-old admitted that most of his current struggles are in his head.

“It’s more mental than anything, I think,” said Walker, who has hit just 37 percent from the field since returning two weeks ago. “Tonight, I got frustrated at myself and it kind of put myself in a bad place. I’m not even a player like that to really get frustrated. I’m more smiling and I wasn’t that tonight.

“I got into my own head and, mentally, I hurt myself,” he added. “I can’t do that for this team.”

Jayson Tatum and Jaylen Brown were their usual selves Saturday night, with Boston’s young stars combining to score 58 points. Theis chipped in with 14 points and some solid D throughout. The third quarter was perhaps Boston’s best of the season, as they held the Lakers to just 19 points and outscored them by 10 to take a seven-point lead into the final frame. The team started to crumble when Marcus Smart went down with a calf injury — turning the ball over seven times in the fourth —  but when Boston trailed by seven in the final 1:40, Tatum brought them back with a pair of tough buckets. Those makes set up the dramatic final seconds of the contest.

But if the Celtics want to succeed this season, they’re going to need Walker to contribute. The team remains confident that he will do so sometime soon.

“Kemba is a great player and he knows that’s a shot he’s going to make,” said Brown. “So we’re going to need him. And he knows that for us to go far, we’re going to need him. So next game, forget about it, move on.”

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“We’re riding Kemba. He’s a really good player who really cares about his team and really wants to be a part of something special with guys that are going to give for each other,” said Stevens. “And sometimes it’s not your night. But more often than not, it is his night and we believe strongly in that.”