Tadej Pogacar's towering domination of this year's Tour de France is once again raising eyebrows in a sport long tainted by the spectre of doping.
The Slovenian has never tested positive for a banned substance and denies any suggestion his performance in the saddle is chemically enhanced.
AFP Sport looks at the issues surfacing in the wake of the 26-year-old's seemingly inevitable assault on a fourth Tour de France.
WHY IS POGACAR SINGLED OUT?
First and foremost because he's the best. He won in 2020, 2021 and 2024 and held a 4min 15sec lead over arch rival Jonas Vinegaard going into Wednesday's 17th stage.
Third-placed Florian Lipowitz was over nine minutes adrift, and Carlos Rodriguez in 10th trailed by almost 21min with five days to go.
Equally at home in the mountains or on flatter stages, Pogacar shrugs off his attackers with nonchalant ease.
Last year he shattered the record time for the climb of the Plateau de Beille set by Marco Pantani in the dark years of the banned blood-booster EPO.
On Tuesday he set a new fastest time for the ascent of Mont Ventoux in southern France.
Pogacar's UAE team frequently has the peloton in the palm of its hand.
Some point to the presence in Pogacar's team of background management figures like Mauro Gianetti.
The Swiss used to be part of the now defunct Saunier-Duval team, which was under scrutiny from anti-doping authorities in the late 2000s.
POGACAR'S REACTION?
Pogacar himself brushes off the suggestions of skulduggery he has had to face ever since his first Tour win five years ago, always insisting that he should be "trusted".
Last October he said to dope "is to ruin your life". "I don't want to take the risk of falling ill one day," he added, pointing out that cycling was "a victim of its past".
He continued, with an air of resignation: "There is no trust, and I don't know what can be done to restore it."
DOPE-TESTING ON THE TOUR
Around 600 blood and urine samples will be collected from the peloton during this year's race, with 350 out-of-competition samples taken in the run-up to cycling's blue riband event.
Drug controls are the responsibility of the International testing Agency, which is independent from cycling's governing body the UCI.
Each day the stage winner and yellow jersey holder are routinely tested.
A selection of the samples are held for 10 years to allow for retro-testing with the advance of new detection techniques.
The UCI also inspects bikes to prevent any technical cheating.
While ketones to help store energy are permitted and widely used, the UCI banned the inhalation of carbon monoxide earlier this year.
RECENT DOPING CASES?
The last rider to be caught cheating was Colombian Nairo Quintana. He finished sixth in 2022, but was disqualified after traces of the banned painkiller tramadol were found in his blood.
BEWARE OF COMPARISONS
Pogacar's ability to smash records set by infamous dopers like disgraced seven-time winner Lance Armstrong or Pantani is remarkable.
But riders warn of the trap of comparing times up an ascent like Mont Ventoux, pointing out that external factors like wind and rain and the pace of the stage.
And as in other sports, cycling has made enormous progress since the EPO years.
Technology has led to faster bikes, with the Tour's technical director Thierry Gouvenou suggesting a there has been a 10 per cent gain in performance just thanks to better two-wheeled machines. Nutrition and training have also evolved.
THE PELOTON'S REACTION
Pogacar's peers appear split, with some – albeit anonymously – questioning the Slovenian's superiority, while others regard him as an athlete the like of which only comes round once in a blue moon.
They compare him to pole vaulter Mondo Duplantis or Usain Bolt, the Jamaican sprint king who rose above a sport tainted by doping to be revered in a class of their own.
The fact that Pogacar displayed unnatural ability from a young age and tends to dominate throughout the season is interpreted by some as a reassuring sign.