It is a sign of the sceptical climate created by Lance Armstrong that when Novak Djokovic came off the court on Tuesday, having confirmed his place in the semi-finals, the questions were less about the smoothness of his backhand than how he could possibly maintain such a mind-boggling level of fitness.
Only two days previously, Djokovic had been pushed to the very edge in a five hour two minute battle with Stanislas Wawrinka. Yet here he was, gambolling around the baseline like a faun and chasing down any number of apparently unreachable balls. Nobody actually asked him if he was popping any magic pills, but they might as well have done.
Faced with this potentially awkward situation, Djokovic responded like the dignified diplomat he has become, rather than the young scamp who would once have hit out angrily at the first sign of suspicion.