By Matthew Geagan, CBS Boston

BOSTON (CBS) — It might be time to get a little worried about the Boston Celtics. Boston lost a frustrating Game 4 to the Toronto Raptors, 100-93, on Saturday night, and now their playoff series is all tied up at 2-2.

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It was not the ideal follow-up for Boston after a heartbreaking loss at the buzzer on Thursday night, as the Raptors simply out-muscled and out-hustled the Celtics throughout. Now Toronto has even more momentum heading into Monday night’s Game 5.

The Celtics kept Game 4 close for the most part, staying in the game by attacking the basket and playing some strong defense. But the Raptors were absolutely on fire from downtown, hitting 17 of their 44 three-point attempts. Even worse were the 24 second-chance points the Raptors scored.

Pascal Siakam bust out of his series slump with 24 points off 10-for-23 shooting and 11 rebounds. Kyle Lowry started hot, hitting his first six shots, and finished strong with 22 points, 11 rebounds and seven assists. Serge Ibaka made some big buckets off the Toronto bench, finishing with 17 points off 7-for-9 shooting to go with seven rebounds in 22 minutes.

Boston was not as hot from deep, hitting just seven of their 35 attempts from three-point range for their worse shooting night of the postseason. They got a lot of solid looks, but the majority of them didn’t fall.

Jaylen Brown was ice cold throughout the game, hitting just two of his 11 shots from downtown. He had 14 points off 4-for-18 shooting in the loss.

“We never really caught our stride or rhythm, and we still had opportunities to win the game,” Brown said after the loss. “For us, we’ll shake it off. It’s 2-2. We’re in the moment and have to make the best of our situation. We’ll come out and be ready to fight.”

Jayson Tatum led Boston with 24 points and 10 rebounds, while Kemba Walker added 15 points and eight assists.

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The Celtics kept it relatively close in the first half and even had a lead before Fred VanVleet hit a three in the closing seconds to make it 49-49 at halftime. Boston struggled again in the third quarter, with Toronto outscoring them 32-24 in the frame. The Raptors have owned the third quarter this series, outscoring the Celtics 122-96 overall in the quarter.

Brown didn’t hit his first three until there were five minutes left in the game, starting 0-for-9 from deep. But his first make made it a 91-86 game and gave Boston a little life, until Kyle Lowry answered that make with a three of his own.

Boston was still in it in the final moments of the game. Daniel Theis was fouled by Marc Gasol as the C’s big man corralled a Tatum missed three. Theis missed both freebies, but Tatum was fouled as he put in a layup off Theis’ miss. Tatum’s three-point play made it a 98-93 game in the final minute.

But Tatum was called for a push-off on Lowry with 32.6 seconds left, and that sealed it for the Raptors.

The Celtics spoke a big game after losing at the buzzer on Thursday night, adamant that they’d bounce back in a big way on Saturday. Game 4 was supposed to prove they had a championship mentality. That did not happen, and now it’s a whole new series at 2-2, with Toronto owning all the momentum.

“I told the team to be down five or six with 48 seconds with the way we played, there are some positives. But we have to play harder,” said head coach Brad Stevens. “It’s about being your best when the best is needed, and we weren’t tonight.”

“They made great plays and had great intensity throughout the game. I don’t think we matched their intensity,” said Walker. “It’s the playoffs, we have to be better. That’s it.”

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All of a sudden, the Celtics will be the team desperate for a win on Monday.