Cavs are no longer perfect and Celtics remain the team to beat

Jayson Tatum led the Celtics with 33 points in their 120-117 victory Tuesday to end Cleveland’s 15-0 start to the season. (Photo by Winslow Townson/Getty Images)

BOSTON — Everyone knew the deal. The Cleveland Cavaliers entered Tuesday’s game against the reigning champions with a 15-0 record, second-best start to a season ever, and it was an NBA Cup game to boot.

“We knew,” said Boston Celtics guard Derrick White. “Everybody knew.”

In front of a national television audience, the Celtics reminded the Cavaliers that the Eastern Conference still runs through Boston. They made five of their first eight 3-point attempts, took an 18-8 advantage midway through the opening quarter and never trailed again in a 120-117 victory Cleveland never quit.

Boston pushed its lead to 65-48 by halftime, making nine more 3-pointers on 11 attempts in the second quarter. We could call it a barrage if it were not so expected. This is what the Celtics do. Their 51.1 3-point attempts lead the league by almost six per game. Even at a middling conversion rate, they sink nearly 20 triples a night. Make it 22 on Tuesday. Better keep up if you ever want that math to work in your favor.

The Cavs could not. They shot 10-for-29 from deep and climbed uphill all night as a result. This was a deviation from their norm. They have been playing faster and with more freedom under new head coach Kenny Atkinson, who learned in his time with the Golden State Warriors that the ball should never stick.

Except it did against Boston. “Not great,” Atkinson said of his team’s preparedness.

“The first thing we learned was the force and physicality,” he added. “They had playoff force and physicality; we had regular-season force and physicality. And that’s why we were down 17 at the half.”

They responded in the second half, trimming a 21-point deficit to 86-84 over seven minutes of the third quarter. Some of it was the Celtics settling for contested 3s, rather than creating open ones. Most of it was the Cavaliers pounding the paint. Whether it was Donovan Mitchell taking Neemias Queta off the dribble or Cleveland’s bigs posting smaller defenders, the Cavs outscored Boston on the interior 60-36.

Credit to Cleveland for not conceding the undefeated record, but the Celtics answered that call, too.

“It’s simple: We just locked in on defense,” said Boston’s Jayson Tatum, who finished with 33 points, 12 rebounds and seven assists. “We’ve been in that situation a million times where it’s time to win.”

So they did, which could be interpreted as a bad sign for the Cavaliers, who considered this game a measuring stick of their seriousness as a contender. But Evan Mobley drew a different conclusion.

“From what I saw out there, we could beat anybody,” said Cleveland’s rising star.

Is that feeling different from last year, when Boston ousted Cleveland in a second-round playoff series?

“Not really, honestly,” added Mobley (22 points, 11 rebounds). “Last year it felt the same way. We were right there. We lost the series, but most of the games we were right there with them the whole time.”

Can beat the Celtics and will beat the Celtics are two different things. For as much positivity as the Cavaliers drew from their first loss of the season, there is this: Boston will soon reincorporate All-Star center Kristaps Porzingis, who unlocks another dimension for a team that won a title largely without him.

The Celtics assigned Porzingis to their G League affiliate Monday. Instead of sending him to Maine, they brought the entire developmental team to Porzingis, so he could simulate serious game action for the first time since his surgery, sources told Yahoo Sports. Attendees were pleased with his performance, which is a) to be expected from anyone relaying that information and b) better than the alternative.

Either way, Porzingis’ return is now a matter of weeks, not months, even if he may not be available when these two teams meet again Dec. 1. That is the next measuring stick. This one fell short for the Cavs, who look different from last season yet still a tier below the fully healthy version of the reigning champs.