Over the last decade, the pursuit of tennis' Greatest of All-Time moniker has become a three-horse race between Roger Federer, Rafael Nadal and Novak Djokovic.
Nadal is currently in the lead with 22 grand slams, while the in-form Djokovic is the closest challenger with 21. However, the Serb may rue his decision to value his vaccination status over GOAT status.
Djokovic has made it no secret that he will not get vaccinated and he's already missed out on the Australian Open where he is a nine-time champion.
With the US Open just weeks away and current US restrictions requiring non-US citizens to be vaccinated for entry, Djokovic's chances at tying up the grand slam race with Nadal at Flushing Meadows seem slim.
This frustrates Lendl, as tennis' history is potentially being undermined by red tape.
"If Novak wins the most Grand Slams despite that (the vaccination restrictions), I think we will have an answer," the eight-time grand slam winner told Italian television channel Nove TV.
"If Rafa wins one more title, I think he will have to answer the question about the vaccination and the fact that Novak could not play. And I don't think that's fair. I'd actually like to see someone have a two, three, four title advantage at the top.
"I don't care who it is, I don't have a favourite. Just for the sake of answering that question, to be clear. And, not to say 'If this man could play, maybe it would be different, your record is not that good.' That is not fair."
In terms of Federer - who has been sidelined by injuries for 13 months - Lendl is not expecting any miracles.
"At the moment, Roger seems to be out of it, because he hasn't played for a long time and he is also the oldest," he said of the Swiss Maestro, who turns 41 on Monday.