Column: Raptors’ defense ran out of steam against the Bucks at the finish of Game 1

You’d probably be too distracted by the size of Giannis Antetokounmpo and Kawhi Leonard, too enamored with their shot-making and ball-handling and trash-talking ability, to notice if you’re sitting courtside.

But from the nosebleed seats at Fiserv Forum, you see one of the most important parts of the Eastern Conference finals unfolding below you on every Bucks possession in their half-court offense.

You can see the Toronto defense beat like a heart, the life of the Raptors dependent on a series of precise contractions and expansions to keep the Bucks from getting easy looks at the basket or beyond the three-point line.

Before Game 1, you could hear in his voice and the slight smile on his face just how difficult Toronto coach Nick Nurse thought it would be to defend the Bucks. Being everywhere on the floor, turns out, is a tough ask.

While most teams with even a low level of analytical influence understand layups and three-pointers, the Bucks put into extreme practice thanks to the driving ability of Antetokounmpo, a tornado of limbs, muscles and seemingly unending potential.

“No, it’s not easy at all. He and the rest of their team make it as hard probably as it is in this league,” Nurse said before Game 1, a 108-101 Bucks victory. “But you’ve got to protect the rim, you’ve got to protect the free-throw line, don’t send him to the line, and you’ve got to contest the shots somehow. … And we’ve got to help. And when you do help, they try to kick it out, and you’ve got to either rotate, right, to contest, or you’ve got to forget the rotation, just hustle. Sometimes it’s not very perfect, the rotations, and you’ve just got to bust your butt and get out there.”

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For more than three quarters of Game 1 on Wednesday, the Raptors were in rhythm.

Any concerns that the team’s hearts were still in Toronto, celebrating a series-winning shot that bounced on the rim four times before delivering Leonard another signature playoff moment, were quickly erased watching them defend from a distance.

You’d see Antetokounmpo try to slash his way into the paint, you’d see the Raptors collapse, and when the ball would get passed out, you’d see them sprint out. Contract and expand, contract and expand, contract and expand.

“I thought our defense was pretty good,” Nurse said after Game 1. “I thought we were executing our game plans really well. I didn’t feel like we were under that much stress.”

But when a heart has to pump that hard for that long in the most important game of the season, there’s probably some limits.

Just three days removed from the emotion of Leonard’s cinematic game-winner, the Raptors started to slow down.

“We started off the game well,” Leonard said Wednesday. “We just didn’t finish it up too great.”

The Bucks hit half of their 10 three-point attempts in the fourth quarter; their other points either all came at the free-throw line or at the rim. After being everywhere in the half-court defense for the first three quarters, the Raptors were suddenly nowhere.

A day later, crammed in a small supply storage room at their hotel in Milwaukee, the Raptors faced the media before an early afternoon film session and owned up to their late-game defensive failures.

“My energy level was not there, but my coaches and my teammates know I can do it,” Raptors forward Serge Ibaka said. “I believe I can do both. I can protect the rim and then go out there and contest the three-point shots.”

There are other things the Raptors can do to even the series in Game 2 — being better on offense certainly being a big one. Missed shots and turnovers allow the Bucks to run, and when that happens, it doesn’t matter how locked in a team is on defense.

But on those other, slowed-down possessions, the Raptors’ heart needs to beat.

As Nurse talked about what happened the night before and what needs to happen in Game 2, Leonard stood impatiently in the doorway, waiting for his coach to wrap up his news conference.

“Come on,” he said.

Next door the Raptors were waiting to begin a film session, the team eager to try to figure out how they can beat longer and stronger.

dan.woike@latimes.com

Twitter: @DanWoikeSports