The Boston Celtics accomplished something that few teams have done this season: They made Giannis Antetokounmpo look human.

For much of Boston’s 112-90 victory over Milwaukee in Game 1 on Sunday, the Bucks’ all-star forward navigated the court like a driver whose GPS was failing to connect. Antetokounmpo pressed the Celtics defense for seams but usually encountered roadblocks, and his struggles to exert his typical MVP-level dominance in the paint short-circuited the Bucks’ offense.

The final damage: Milwaukee ceded home-court advantage in the second-round series, and the 22-point defeat was its worst of the season. After a dream season in which Antetokounmpo led the Bucks to 60 wins, he suddenly finds himself at a crossroads against a physical and experienced defense that is completely focused on stopping him.

Antetokounmpo isn’t Michael Jordan, and these Celtics aren’t the “Bad Boys” Detroit Pistons of the late 1980s, but Game 1 saw a “Giannis Rules” defensive strategy in full effect.

Boston’s comprehensive approach is built around exploiting Antetokounmpo’s few remaining weaknesses: his lack of a knockdown jumper and his good-but-not-great vision. Their principles include keeping him out of transition, shadowing him inside the arc with versatile big man Al Horford, heavily contesting every shot attempt in the paint and sending carefully timed help to disrupt his drives and disguise his passing lanes.

“They were loading a lot of guys in the paint,” Antetokounmpo said. “Whenever I got in the paint, when I spin or try to change direction, the second guy was right there. If they are going to play like this the whole series, I have to be able to make the right pass and trust my teammates to knock down shots.”

In recent years, Horford has emerged as one of the NBA’s premier Giannis stoppers because he’s mobile enough to follow Antetokounmpo’s drives, long enough to contest shots in the paint and disciplined enough to avoid fouling out of frustration.

“He knows my moves,” Antetokounmpo admitted.

In Game 1, Antetokounmpo shot just 7 for 21 for 22 points, and the Bucks were outscored by 24 points during his 34 minutes. He was blocked five times and converted just 4 of 14 shots in the paint, well below his season average. Boston ran away with the win thanks to 26 points from Kyrie Irving and 20 from Horford.

“We all understood how we needed to defend and how dangerous [Antetokounmpo] is once he’s in the paint,” Horford said. “For the most part, everyone was very aware. Our guards did a good job of helping and closing down lanes. We wanted to challenge and contest every shot as best we could. We were able to do that.”

As the second half unfolded, Antetokounmpo appeared to be searching for answers. Milwaukee’s shooters did him no favors with a poor showing, leaving Antetokounmpo to take matters into his own hands. A career 28 percent three-point shooter, he repeatedly turned to his outside shot and hit three three-pointers.

If Antetokounmpo is forced to keep making that choice, though, Boston should win the series. Milwaukee’s superstar must play inside-out rather than outside-in, or else he won’t receive enough help from a supporting cast that is largely reliant on his kick-out passes.

“We need to make the game easier on him and easier on ourselves,” said Khris Middleton, pointing to the Bucks’ 13-for-39 shooting from beyond the arc. “I think we hesitated some. Credit to Boston’s defense. Their rotations were on point. They made us second-guess a lot of our actions.”

In addition to improving their outside shooting and forcing more turnovers to create fast-break chances, Milwaukee’s list of possible fixes includes utilizing Antetokounmpo off the ball more to start possessions. Greater variety could help prevent Boston’s paint defense from setting up so comfortably in preparation for his drives, allowing Antetokounmpo’s improvisational skills to shine.

But Antetokounmpo also will need to make quicker decisions, whether timing his forays from the perimeter or working in the post. The Celtics repeatedly capitalized when he deliberated, flashing extra help to contest his shots or clog the paint. From Boston’s perspective, the more Antetokounmpo thinks and surveys, the better.

“As great as he’s been this year, he hasn’t been perfect every night,” Bucks Coach Mike Budenholzer said. “I think Giannis will play better.”

It’s a sign of immense respect that Antetokounmpo has inspired such careful and thorough attention from an opponent with championship aspirations. How he adapts — and whether he can break Boston’s “Giannis Rules” to win a war of attrition — will determine the winner of this series.

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