Speaking on the
podcast In de Waaier, Zonneveld said: "It is always possible that doping is involved, but I wouldn't vouch for anyone. But then he would be the only one with a doping substance that would make him better in every area. I don't know what it would be then."
Stressing the need for evidence before levelling accusations, Zonneveld thinks there is none. Pointing to the world champion enjoying success at underage levels before joining the UAE project, Zonneveld notes that a number of factors could explain his increasingly dominant displays.
Zonneveld says there's no evidence to support accusations
"If you make such accusations, you must be able to prove it. And there is exactly zero evidence."
He added: "Then he went to UAE, which I still find a strange choice, because UAE was a team with money back then, but not with good guidance, or something like that. He eventually found a place there where they could guide him in the best way."
The sport's evolution means that nutrition, training and recovery have taken massive leaps in recent years. Riders now ingest higher numbers of carbohydrates than ever.
He said: "In five years, we have moved from 60 grams of carbohydrates per hour to 120 grams. And what if we start adding lactate to gels? Then you can buffer away even more lactic acid. The development is not yet complete. This is also because a number of very wealthy teams have emerged, which have entered a kind of arms race."
No explanation for continued inprovements
Nonetheless, Pogacar's improvements have put him a step above most of the peloton. His remarkable tendancy to stay fit and healthy while racing is also a noticeable advantage as his career blossoms.
Zonneveld noted the reactions of his fellow professionals and the effect it has had on their motivation.
"But the fact that he has continued to develop physically in this way... Sometimes you simply have no explanation for something. Other than the fact that he is never sick or rarely falls, allowing him to keep building up."
He concluded: "I don't know if he isn't using doping, but I'm certainly not sure that he is. But that question about his dominance is definitely on people's minds in the peloton. Some make a joke of it, others shake their heads when they see their deficit in a mountain stage like that."