Giannis Antetokounmpo is known in many NBA circles as one of the best defenders. Antetokounmpo has the size and length of a big man while retaining the quick athleticism of a guard. Antetokounmpo can protect the rim, but also bother shooters with his length. His physical attributes definitely help him with defense, and most fans would assume that he's a lockdown defender who can guard anyone.
Recently, Kendrick Perkins claimed that Giannis Antetokounmpo isn't quite the lockdown defender that people perceive him to be: in fact, Perkins seems to opine that Antetokounmpo isn't actually a good all-around defender.
Kendrick Perkins seems to think that Antetokounmpo isn't good as a man to man defender: that he can't lock people down when playing one on one defense. Perkins doesn't deny that Antetokounmpo is a good help/free safety type defender, rather, he seems to think that Antetokounmpo isn't that good at locking down other elite offensive players. In the video within the tweet, Perkins claims that Giannis didn't want to guard James Harden or Luka Doncic:
He's not guarding nobody, and everybody around the league knows that. I watched Giannis last year in the bubble: he ran from James Harden. He ran from Luka.
While Giannis Antetokounmpo may have some issues on the defensive end, he is still a widely recognized elite defender, making three All-Defensive teams during his time in the NBA. Perhaps in the coming season, he can convince Kendrick Perkins that he can lock down anybody and stop them from scoring.