Now 76-years-old, Thevenet said he had never before witnessed a rivalry such as the one Pogacar and Vingegaard have engendered.
Thevenet won the Tour in 1975 to end the reign of Eddy Merckx and won a second one in 1977, before mentoring Stephen Roche to glory as a team director.
Analysing Wednesday's eventful struggle between the top four, including Remco Evenepoel and Primoz Roglic, Thevenet came up with a novel angle.
"When Pogacar attacked, we were afraid he was about to kill the overall standings," he said at Thursday start-town Aurillac.
"But then we saw that Vingegaard was up to it and not only that, but that they were ready to work together to get rid of the other two."
Pogacar and Vingegaard have won the past four Tour de France, with the Dane claiming the past two by outfoxing the Slovenian UAE rider.
But Thevenet feels this rivalry has been somewhat put to one side in face of the threat of a broader field of favourites.
"You got the feeling they wanted a mano-a-mano like the good old days, so that later they could fight it out between themselves," said a smiling Thevenet.
"Evenepoel and Roglic may have expected to find an ally in Vingegaard," he explained.
"But it hasn't turned out that way at all, instead he allied himself with Pogacar."
The pair ended stage 11 in a photo finish, yet still managed to put around 30 seconds between themselves and the other members of the Fab Four on the Tour.
"That's his choice, he knows what he has to do to win," Thevenet said of the two-time defending champion.
The Frenchman subscribes to a popularly held belief that Wednesday's stage proved Vingegaard was back to top form.
"At the end, we suddenly saw that Pogacar had to climb up out of his saddle because he was tired, very tired.
"Did he do too much when he attacked or what? Maybe he felt superior to Vingegaard and was stunned by how Vingegaard stood up to him.
"It certainly bodes well for the future of this Tour in the Pyrenees and the Alps," Thevenet added.
He also said that both the unique rivalry and Pogacar's modus operandi were attracting a new generation to cycling.
"There have been other rivalries between two riders, but what makes this one different is this - what I admire is that Pogacar shows such willingness to make efforts to win this Tour from a greater distance.
"That is to say traditionally they are used to seeing rivalries that heat up in the final week.
"Pogacar going for it in the first week is good for cycling and it's bringing lots of new fans to cycling," Thevenet concluded.
The contenders for the title have two big mountain stages to look forward to in the Pyrenees this weekend.
