Kahleah Copper was ready for the WNBA playoffs. But in a Game 1 beatdown, the rest of the Chicago Sky were not.

Wednesday was not Kahleah Copper’s night.

The three-time All-Star scored only 15 points in the Chicago Sky’s WNBA playoff opener against the Las Vegas Aces as the reigning champs cruised to an 87-59 blowout win. Copper turned the ball over three times, made only one 3-pointer and didn’t score in the fourth quarter.

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It wasn’t a great performance — and Copper shouldered responsibility.

But she was restricted by lackluster contributions from every other Sky starter.

Alanna Smith picked up three fouls in the first quarter. Marina Mabrey disappeared. The rest of the Sky roster besides Copper went scoreless for more than eight minutes between the first and second quarters as the Aces ripped off a 21-8 run to take a 19-point lead.

By that point, the game was as good as finished.

Copper is an undeniable star, but the loss set clear perimeters on her limits — and a checklist for the Sky in the offseason, whether that begins after Game 2 on Sunday or later.

Outside of Copper, the remainder of the starting lineup combined for 28 points — only one more than the Aces scored in the first quarter alone. The Sky took only eight free throws — six by Copper, two by Smith — a reflection of their inability to pressure the rim. And the Aces did it without relying on their best player; three Las Vegas players topped A’ja Wilson’s routine 14-point performance.

Without any other offensive threats to patrol, the Aces were content to clamp down on Copper, the only Sky player to score in double digits.

“We got our ass beat, I’m not going to lie to you,” said veteran guard Courtney Williams, who finished second behind Copper with nine points.

While the entire starting lineup struggled to stand out, a timid shooting night from Mabrey was the gravest limitation on the Sky’s scoring.

Mabrey scored only seven points on 3-for-10 shooting, including 1-for-4 behind the 3-point arc. She took only two shots in the first quarter and didn’t attempt a 3 until less than three minutes remained in the first half.

Mabrey’s absence cuts deeper in light of what the Sky gave up to acquire her — four draft picks spread over three seasons — in a trade made by former coach and general manager James Wade, who left the Sky to shoulder the gamble for the next three years.

The trade put almost unfair pressure on Mabrey, whose performances will be measured against the potential of those draft picks. But Mabrey is still the Sky’s No. 2 player, and they won’t succeed in any future postseason outings if she can’t live up to that expectation.

Even if her shots aren’t falling, Mabrey’s role as a perimeter shooter is key to the offense. The undersized Sky thrive by slashing to the hoop — and they can’t get to the rim if they aren’t stretching the court at the 3-point line, a responsibility that falls first to Mabrey.

The poor shooting highlighted other glaring weaknesses in the Sky’s roster construction, including the lack of a committed point guard and an undersized paint presence. But none of these issues can be shored up until the Sky determine the future of their coaching position.

Wednesday marked the playoff debut for interim coach Emre Vatansever, who stumbled through decisions such as leaving Smith in the game to pick up her third foul in the first quarter.

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The Sky have to find success by controlling the margins of matchups, which requires a high level of discipline from a coach’s plan and in-game decision making. Without this sharp guidance, a familiar truth prevailed in Game 1: Once the Sky are lost, they can’t find their way back into a game.

It’s unsurprising that an interim coach making his postseason debut would be overwhelmed. But the aimlessness of Wednesday’s loss highlights why the Sky need to seek a seasoned coach for the future.

It’s also unsurprising that an eighth-seeded team would struggle against the Aces, who went 34-6 in the regular season, including 19-1 at home.

Still, this series can teach the Sky a lesson — but it’s up to the front office to learn what’s necessary to equip a playoff-ready team next year.