The image from Game 1 of the Western Conference Finals that should keep coach Mike D’Antoni up at night is not Kevin Durant taking fadeaway jumpers right over the top of P.J. Tucker, or even Stephen Curry working hard and getting a couple of steals off James Harden as the Rockets tried to isolate him on defense.

No, Houston’s nightmares should be filled with Klay Thompson hitting wide open, uncontested three after uncontested three.

Klay had himself a night 👌💦 pic.twitter.com/sL8gp2tHQe — Golden State Warriors (@warriors) May 15, 2018

Thompson took 18 shots in Game 1 and only four were contested (according to the NBA’s tracking data). He finished with 28 points and six made threes on 15 attempts. All game long Harden — the primary defender on Thomspon much of the night — either got burned by Thompson on cuts or just lost him as he tried to switch and help on others. Nine of Curry’s 15 shots were also uncontested. Harden, despite his 41 points on one end of the floor, was a defensive mess that the Warriors targeted all night long in Game 1.

A lot was made — both on the national broadcast and in writing out of that game — about the Rockets isolation-heavy offense and how the Warriors defended that. It is worth some discussion, although that is precisely how the Rockets have played all season — slowing the pace (they were 14th in the NBA) and hunting out mismatches with Harden and Chris Paul, two of the best isolation players in the game. Points for everyone else came off those actions. That is who the Rockets are now.

The Rockets bigger problem in Game 1 was their switching defense — the Warriors had a 118.4 offensive rating for the game (points scored per 100 possessions, stats via Cleaning the Glass), with a ridiculous team true shooting percentage of 65.4.

If the Rockets can’t do a better job of getting stops, this is going to be a short series.

“When you get this deep in the playoffs, it’s all about defense. You have to be a great defensive team to win a championship,” Warriors’ coach Steve Kerr said after the game. “You just have to be.”

The Rockets had the sixth-best defense in the NBA in the regular season, but they looked nothing like that in Game 1. They couldn’t get the ball out of the hands of Durant, Curry, or Thompson.

The Warriors three best players — three of the best shooters/scorers in the game today — were able to get up 60 of the Warriors 80 shots in this game (and a combined 26 three-point attempts). If the best scorers in the world get to take 75 percent of the team’s shot attempts, the Warriors are going to win. Meanwhile, the guys most teams want to force to shoot didn’t have too much: Andre Iguodala took just three shots, Draymond Green five, Kevon Looney one. Every game one of the Warriors’ big three is going to get up a lot of shots, but if all three of them do (and a lot of those looks are not contested) it’s going to be a long night.

“(Durant is) seven feet, shoots falling away, he’s one of the best scorers ever, right?” D’Antoni said. “I thought he was extremely good. We can withstand that. We can’t withstand turning the ball over, missing layups, Klay Thompson got up 15 threes — he can’t get up 15 threes. We’re switching everything and staying out for that reason. So we have to clean up some stuff.”

All season long the Rockets switched everything defensively — every on and off the ball pick, even when they didn’t have to — in preparation for this series. Against the Warriors’ versatility switching is needed and must be seamless. Houston did not do that in Game 1.

The Rockets did do a couple good things defensively, such as limiting the Warriors in transition. Golden State started 15.3 percent of their possessions in this game in transition, a much lower percentage than in the regular season (when the Warriors were north of 20 percent). However, when the Warriors did run they were very efficient, scoring 114.3 points per 100 possessions (stats via Cleaning the Glass).

It was not enough. The Rockets need to be much better in Game 2.

The Rockets need more Clint Capela on Wednesday night — he had a couple of blocks and played respectable defense in this game.

More than that, the Rockets need better team defense from guys like Harden, Paul, Trevor Ariza, Tucker and the rest. They need to contest shots, and they need to not let the Warriors best shooters — again, some of the best shooters in the game — take the 75 percent of the team’s shots.

The Rockets will score more points in Game 2 and going forward in this series. They will find their spots against the Warriors defense.

None of that will matter if Houston doesn’t get more stops. Defense is going to win them this series.