Sixth overall, despite riding in Chris Froome's service, the 29-year-old Welshman has been a marvel in the mountains, perfect on the pave and a wizard in the wind.
But he is also a double Olympic and triple world champion on the track, with the 4,000m team pursuit his speciality. And that, for some, is a problem.
Michael Rasmussen, the doping Dane who was thrown out of this race while leading in 2007 for lying to his team, is back at the Tour working for a newspaper.
Nothing unusual about that - there are ex-dopers around almost every corner here, working in one part of the Tour circus or another - but the man known as "Chicken Legs" for his skeletal frame, announced his arrival with a tweet during Thursday's 12th stage to Plateau de Beille.
"Geraint Thomas, a track rider, is catching up with a Colombian climber, Nairo Quintana!" wrote Rasmussen, who has confessed to cheating throughout his road career, as Thomas closed down a Quintana attack.
