I'm not asking him to defend against Zidane, he's got Ballack here. A top notch midfielder, yes, but nothing he hasn't defended against before.
Seedorf and Keane do take the "heavy lifting" as you call it, the wings are my problem not the middle. If my opponent's only serious goalthreat is a long ranger from Ballack who has Veron defending against him, I can manage that.
Again, the basic thought is that Veron isn't defending against a top attacker - Zidane, Platini, Baggio, Iniesta or even Rui Costa, it's Ballack! He is a central midfielder who happens to be really good going forward. Veron isn't the best defensively and is pretty lazy there, but he can manage the job of preventing Ballack from scoring a long ranger, I'm not even remotely suggesting that he will stop Ballack completely, but he can definitely limit him at some level. Edgar, Raees and some other people talk as if he doesn't do anything defensively, just sit there and watch the midfield get overrun until we get the ball back.