The Celtics looked like they had their 12th straight win in the bag Tuesday night in Cleveland.

But Boston took its foot off the gas too early, and the Cavaliers made the visitors pay.

The C's swelled their win probably to 99.9% at Rocket Mortgage FieldHouse when a Jayson Tatum bucket with nine minutes to play gave Boston a 22-point lead. But the NBA's best team, which hadn't lost since Feb. 1, allowed the Donovan Mitchell-less Cavs to storm all the way back and ultimately secure a 105-104 win.

After the game, All-Star guard Jaylen Brown issued warranted criticisms of his team for its poor late-game effort.

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"We are a much better team than we showed (Tuesday), and today was just a mentality loss, I think," Brown told reporters, per MassLive. "We had the game and then we got comfortable, so it was more of a mindset thing than Xs-and-Os. We gotta just be the more disciplined, the more militant team to be focused. We weren’t that -- usually we are that -- and we felt that (Tuesday) and I think that's the reason why they were able to get back into the game, because our mindset was a little bit too lax and we were too careless with the ball."

Brown added: "You put yourself in that spot when you don't put a team away, don't match the gas. We should've matched the gas when we was up 22. We kind of let them hang around, it was cool, and comfort will kill you. And I think we needed that. I think that's good, that keeps us on our toes and keeps us being able to learn and move forward."

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It probably was time for a reality check for the Celtics, who thoroughly embarrassed their opponents throughout February. Wake-up calls and frustrating losses can serve as very helpful lessons for a team with arguably the most legitimate championship aspirations in the league.

Returning to the win column Thursday night won't be easy, though. Boston is set to kick off a four-game West Coast road trip in Denver against the reigning champion Nuggets.

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Featured image via Ken Blaze/USA TODAY Sports Images