Zion Williamson with an open lane to the rim is an automatic dunk against 99 percent of the NBA. Just not against Giannis Antetokounmpo.

The proof came halfway through the second quarter of last month’s clash between the Pelicans and Bucks. Zion saw Josh Hart steal the ball from Khris Middleton and immediately started sprinting the other way. Giannis took a half-second to slow down Hart in transition before turning around to run with the rookie sensation.

The play would have already been over against anyone else. Not many players can keep up with Williamson when he has a full head of steam. Even fewer can jump with him. And there might not be another player in the league who can absorb a bump from him in midair.

Giannis made it all look easy. He enveloped Zion with his massive wingspan, didn’t budge an inch when Zion lowered his shoulder, and sent the Pelicans star’s shot flying out of bounds.

It’s easy to miss just how impressive Giannis’s defense is in real time. So I slowed down the clip to one-quarter speed the second time around:

Zion is putting up numbers that we haven’t seen since a young Shaquille O’Neal terrorized the league in his rookie season. His game against Giannis has been the one exception: He shot 5-of-19 (26.3 percent) from the floor against Milwaukee and has gone 132-of-212 (62.3 percent) against everyone else.

Against the reigning MVP, Zion couldn’t just dominate on strength and athleticism alone. Questions that usually don’t matter suddenly became urgent. Does he have a right hand? Can he shoot off the dribble? Can he thread passes through tiny windows?

Circle every one of Zion’s upcoming games against Giannis every season going forward. They will show just how much the phenom has worked on his game, and how much work he still needs to do.

Giannis is the apex predator in the NBA. Any game between him and another star becomes an event if he decides to guard them. It doesn’t matter who it is, what position they play, or what their strength is. He can guard anyone.

He’s the end point of an evolutionary line. Big men have been getting longer, quicker, and faster for a long time. But it’s hard to imagine a 7-footer improving on Giannis in those categories.

The Greek Freak had unlimited defensive potential when he came into the league. He just needed to get stronger. Giannis was a raw collection of skinny limbs at Zion’s age. Now, at 25 and in his seventh season in the NBA, he has bulked up and filled out.

The result is one of the most versatile defenders in the history of the game. Giannis has the speed to defend point guards, the strength to defend centers, and the length to bother anyone in between.

It’s almost impossible to score on him. He’s in the 99th percentile of players league-wide this season when defending isolations. He has faced all kinds of challengers, and it always ends the same way. Look at how naturally he guards three players as different as Zach LaVine, Jayson Tatum, and Joel Embiid in this clip:

He’s also playing a bigger role in Milwaukee’s defense than ever before. The Bucks have the lowest defensive rating with any of their rotation players when Giannis is on the floor (96.5 in 1,668 minutes) and the highest when he’s off the floor (103.4 in 1,222 minutes).

Mike Budenholzer’s scheme is built around his star’s unique abilities. The Bucks protect the rim as well as any team in NBA history because they play two centers at the same time without giving up any speed. Giannis is essentially what would happen if Rudy Gobert were a power forward who could defend all five positions.

He can even anchor the defense on his own, a new twist the Bucks have added this season. They have a net rating of plus-27.8 and a defensive rating of 89.1 in 254 minutes when Giannis has played without a traditional big man next to him.

As the centerpiece of the league’s no. 1 defense, Giannis could become only the third player to win MVP and Defensive Player of the Year in the same season. The other two were Michael Jordan and Hakeem Olajuwon.

There’s more to being the best player alive than being able to score 30 points. A lot of players can do that. Two-way ability is what separates the best players in the postseason. The few guys who can drop 30 and guard the best player on the opposing team have a huge advantage.

Giannis learned that firsthand. Milwaukee was up 2-0 and running away with last season’s Eastern Conference finals when Kawhi Leonard began guarding him in Game 3. Kawhi’s ability to slow him down helped Toronto win the next four games and ultimately the NBA title.

There has been a lot of talk about how much Giannis has improved on offense since then. He didn’t have a Plan B when Kawhi pushed him out of the lane. Now he’s making more 3s than ever before and has added a turnaround jumper to his game.

But there isn’t enough talk about what didn’t happen on the other end of the floor in that series. Budenholzer never put Giannis on Kawhi. He stuck with his normal defensive strategy and kept Giannis as a help-side defender at the rim, which meant that his best individual defender could do nothing as Kawhi turned the midrange area into a personal layup line.

That should never happen again. Budenholzer has the ultimate defensive adjustment in his back pocket. He just has to be willing to use it.

The Bucks have a lot of good defenders on their roster, from Eric Bledsoe at point to Wesley Matthews and Khris Middleton on the wing and the Lopez twins at center. But none of them can do as many different things as Giannis. If someone on the opposing team heats up, he can put out the fire.

Look at what Giannis has done as the primary defender against other elite players this season:

Giannis vs. Other Stars Player Possessions Field goals Player Possessions Field goals Ben Simmons 53.6 0-for-1 Pascal Siakam 53.4 7-for-16 Anthony Davis 25.4 3-for-12 Zion Williamson 16.8 1-for-7

Those matchups will be even more important to win in the postseason. Giannis can guard Jimmy Butler against Miami, Ben Simmons or Joel Embiid against Philadelphia, Pascal Siakam against Toronto, and Jayson Tatum or Gordon Hayward against Boston. Make it all the way to the NBA Finals and he could guard either Kawhi or some combination of LeBron James and Anthony Davis.

Milwaukee can change the dynamic of a series just by sliding Giannis around the floor. That’s the key to winning year after year in the playoffs.

LeBron’s run of eight straight NBA Finals appearances began in 2011. Miami was down 1-0 to Chicago in the East finals when he began guarding Derrick Rose, the reigning MVP. All of the advantages that Rose had against opposing perimeter players were gone in an instant. LeBron could move just as well as any guard—and he was 6-foot-9.

James Harden caused a fuss last week when he said that he was more skilled than Giannis because he wasn’t a 7-footer who could just dunk on people. He wasn’t completely wrong, but the argument doesn’t matter. There are no weight classes in basketball or bonus points awarded for degree of difficulty. Giannis has physical gifts that no one else has. The best way to leverage them is on defense.

Giannis can guard Harden but Harden can’t guard him. That two-way ability is his ticket to basketball immortality. And it’s why this spring could be the beginning of the Giannis era.

Statistics current through Sunday’s games.