the strength of his shoulders, forearms, wrists & hands. And really work on his sprinting.
He could probably use some intense tumbling drilling, too. He's light on his feet, & has good closing speed — but his upright posture really doesn't allow him to extend as quickly as he should.
He's the type of "stiff" that can be in no small way corrected, imo. He just needs to put in the work.