NBA players love to tell their opponents how unguardable they are. It's easy to understand why. The whole idea of defense is to prevent the guy with the ball from putting the ball through the hoop, and there is no simpler way for the guy with the ball to explain that his defender is incapable of stopping him from doing just that than to look the defender in the eye and say, "You can't guard me." It's a demoralizing taunt that leaves little room for an effective retort, because the box score is always going to reveal the truth.
"You can't guard me" means different things when said by different people, though. When Kevin Durant says it, it might mean that the player who is defending him is simply too short to bother Durant's jump shot. When Joel Embiid says it, it might mean that the guy trying to defend him in the post just isn't strong enough to keep himself from getting backed under the rim. When Russell Westbrook says it, it means that Russell Westbrook is lying. There are a lot of great scorers and trash talkers in the NBA, but I don't think anyone has a more justified claim to the "You can't guard me!" taunt than Ja Morant, who is unguardable in the purest sense of the term.
Morant has spent a lot of time telling opponents that they can't guard him during the first two games of his team's second-round series against the Warriors. He's had good reason to do so, as he scored 34 points in a Game 1 loss and 47 points in a Game 2 win. In Game 2, Morant scored his team's final 15 points and did so while facing a defense totally focused on trying to stop him. Morant is not the kind of player who can undo a defense with unlimited shooting range, nor does he possess the brawn one needs to outmuscle multiple defenders and get to the rim. What he does have is quickness, a whole goddamn lot of it, and it's that speed that allows him to continue scoring even when there are five opponents on the floor all set on preventing him from doing just that.
This, to me, is what makes Morant the most purely unguardable player in the league. There's no gimmick, or reliance on size and strength. There's just one guy getting to a spot much faster than anyone else can, and then the next spot, and the next one, and so on until the ball is falling through the net and the defenders are trying to figure out what exactly just happened. What else is there to say about a guy who moves like that, other than, "They can't guard him."