For the second succesive season, the Boston Celtics stormed into Oracle Arena and upset the Golden State Warriors on Wednesday. The Celtics went on a 21-5 run late in the game and held the Warriors to 12 points in the fourth quarter, earning a 99-86 victory. Isaiah Thomas scored a team-high 25 points on 7-of-20 shooting for Boston, but this victory was more about defense. The Celtics’ effort was there on the defensive end all night, and they hung around until Golden State fell apart. The Warriors have lost three of their past five games, and the second-place San Antonio Spurs are only two games behind them in the standings.

Takeaways:

I wish these teams played more than twice a year

Boston always plays Golden State hard. Coach Brad Stevens has conditioned his players to not get discouraged when Stephen Curry and Klay Thompson make big 3s, and the Celtics have a small army of versatile, tough and competitive defenders who hound the Warriors all game. Typically, Boston keeps it close and then, when it comes down to half-court execution at the end, it genuinely believes it can make more plays than the Warriors.

I love the way Avery Bradley and Marcus Smart defend Golden State’s guards. I love that Curry and rookie Jaylen Brown had a bit of a tiff over trash talk. Both teams spread the floor all game, move the ball like crazy and try to cause turnovers. I’m not saying I would prefer this to Warriors-Cavs III, but it would be nice to get more than two of these matchups every year.

The Durant effect

When Kevin Durant got hurt, Golden State coach Steve Kerr said the team would basically play the same way, but had less room for error. He had noticed some slippage when it came to the little things -- boxing out, off-ball defense, recovering loose balls -- and also knew the Warriors would have a tougher time creating good looks late in the shot clock. Durant has been by far Golden State’s most consistent offensive player, and when his teammates have been cold, he has usually come to the rescue. This time, the Warriors shot 6 for 30 from deep and no one was there to bail them out.

Durant’s absence also messes with Kerr’s normal rotations. For a stretch in the fourth quarter, Curry was out there with Ian Clark, Patrick McCaw, Andre Iguodala and James Michael McAdoo. That was when the Celtics pushed their lead to double figures. Which brings us to ...

Boston is the deeper team right now

The Celtics got solid minutes from reserves Kelly Olynyk, Jonas Jerebko, Smart, Brown and Terry Rozier. The Warriors got a nice boost from Iguodala in the first half, but in general couldn’t find a rhythm when their stars weren’t on the court together. Curry had 23 points on 8-of-16 shooting, Thompson had 25 points on 11-of-23 shooting and everybody else combined for 38 points on 18-of-45 shooting. Golden State still believes in “strengths in numbers” as a mantra, but it appeared to be outnumbered here.

(It would be a mistake to look at these numbers and place the blame on Draymond Green, who scored 13 points on 6-of-15 shooting. Green’s shot obviously wasn’t great, but he was everywhere, finishing with eight rebounds, two assists, three steals and three blocks. The Warriors just needed more from the supporting cast.)

Golden State looks tired

Part of this is that Boston just tires its opponents out. It’s difficult to play against an extremely physical team that stretches your defense for a full 48 minutes. This has been an under-discussed aspect of Thomas’ fourth-quarter heroics this season, and it was evident here. The sloppy Warriors turned the ball over eight times in the final frame, which is a credit to the Celtics defense, a sign of mental fatigue and the most concerning trend about their season.

This is where I must point out Golden State is in the middle of a weird stretch of schedule that Kerr called the most insane he has ever seen in his career. This wasn’t a typical home game -- the Warriors played a back-to-back in New York and Atlanta on Sunday and Monday, and they will head back on the road for a back-to-back in Minnesota and San Antonio on Friday and Saturday. They won’t use this as an excuse, but it has to be a factor. Kerr acknowledged as much postgame and said that resting players against the Timberwolves is a possibility, via the San Jose Mercury News’ Anthony Slater.

The plus-minus hero

Individual game plus-minus is a noisy stat, but it’s not a coincidence that Olynyk was plus-29 in this one. He finished with 17 points on 7-of-9 shooting, plus five rebounds, five assists and three steals. I have never seen him play better.

Everyone knows Olynyk is skilled with the ball in his hands, but the thing I like most about him is his efficiency of movement. He makes quick decisions, and whether he’s firing off a pass or hitting a reverse layup over a longer defender, he always seems to have perfect touch. He gave Golden State problems from all over the court.