Here are five things were learned about the Warriors during a 92-88 loss Thursday night in Boston.
1) CAN'T ALLOW THE CELTICS TO BREATHE
This was going to be the toughest game of the season, and they knew why. It was the day after a cross-country flight, in a place known for hostility toward visitors and, above all, against a Celtics team coached by Brad Stevens.
Every time the Warriors have played the Celtics since Stevens arrived in 2013, the Warriors have had the superior roster. Yet the Celtics generally are able to make them and keep them sweating for most of the game's duration.
The Celtics know that. Down 17 with 5:25 left in the second quarter, they got within five at the half. Down 17 with 4:59 left in the third quarter, they went on a 19-0 run to take a lead inside the final minute of the quarter.
The Bucks and the Heat disrupt can Warriors' offense enough to hang around. The Spurs and Grizzlies can at times make things tough for Stephen Curry and Klay Thompson. Only the Celtics can consistently do both.
2) WARRIORS DIDN'T ADAPT TO THE WHISTLES
The officials -- chief James Capers, Pat Fraher and Tyler Ford -- were at best a middling crew by NBA standards. Capers is an ordinary lead, Fraher a mediocre No. 2 and Ford one of the weakest officials in the league.
The Celtics are a physically aggressive team. That's particularly true of Marcus Smart, Marcus Morris and Jaylen Brown, each of whom plays as if gunpowder is running through his bloodstreams. On a normal night, they practically dare referees to call fouls. On this night, with this crew, they were in heaven.
The Warriors were, by contrast, in purgatory. Never adjusting and rarely matching Boston's physical intensity, the Warriors were outrebounded 52-47 and, moreover, lost the second-chance points battle 18-5.
The Celtics earned their decisive 38-19 margin in free throw attempts.
3) CAN'T CRUISE AGAINST CONTENDERS
The Warriors, supremely confident, will go through stretches of a game where they simply lose interest or focus. There is a growing belief within the league that they will allow comebacks.
That belief is based in fact, at least as it pertains to the league's better teams. The Warriors led the Pistons by 14 and lost by eight, led the Grizzlies by five and lost by 10, led the Rockets by 17 and lost by one.
Nuggets coach Michael Malone reminded his players of that on Nov 4 in Denver. They wiped out an early 13-point deficit to go up by 2. It didn't last, but . . .
Now this. The Warriors can look say they should have won all four of their losses. Quality opponents can look back and believe the Warriors are lack killer instinct.
They had it during 2017 playoffs. Maybe they're waiting for the REAL season.
4) STEVE KERR SOMETIMES HAS TOO MUCH FAITH
The coach believes in his team, as well he should, for it has rewarded him with three consecutive appearances in the NBA Finals and two championships.
That said, there was no emphatic response to the Warriors giving back 12 points of a 17-point lead in the first half and all of a 17-point lead in the third quarter.
Kerr called a timeout at the 3:17 mark of the second quarter, after Boston whittled a 44-27 Warriors lead down to 45-34. There was no timeout over the remainder of the half, which ended with the Warriors leading 47-42.
Another timeout was called with 3:46 left in the third quarter, after the Celtics shrunk the 17-point lead to 10, 66-56. Out of the timeout, Boston went on a 12-0 run, taking a 68-66 lead with 53.8 seconds remaining in the quarter.
The game was arrhythmic. The officials seemed overmatched. Kerr, believing in his players and anticipating a close game down the stretch, wanted to save his timeouts. He used them all, but one timeout during a 19-0 run seems sparse.
5) STRANGE FEAR OF THE CUP
Boston plays tremendous team defense, but the Warriors made it easy on the Celtics, particularly down the stretch by forgetting they have no rim protector.
The Warriors were 7-of-21 from the field in the fourth quarter. Within that they were 3-of-12 from deep. They fired four triples for every three shots in the paint. Six of the eight shots they took over the final 2:21 were from deep.
We know the Warriors love the 3-ball and that it has been very good for them. But in a close game featuring mediocre officials, they settled for long jumpers rather than going right at one of Boston's few defensive weaknesses. The Celtics rely on team defense because they rank 24th in blocks.
The Warriors, to be sure, shied away. They feared when there was nothing to fear.