After squandering two set points in the opener on a blustery Court Suzanne Lenglen, Djokovic's renowned fighting spirit ebbed away quickly and he surrendered the third set in 20 minutes.
The result was all the more remarkable as in five previous matches with the 23-year-old he had lost one set and last month thrashed him 6-1 6-0 in Rome -- a result that suggested Djokovic had found his mojo, missing since he won the French a year ago.
Sixth seed Thiem, who to be fair played superbly in the first set but must have thought he was facing a Djokovic impersonator thereafter, is yet to drop a set at this year's tournament but his next task is a daunting one.
"It doesn't get any easier," Thiem, beaten by Djokovic in last year's semi-final, said on court when asked to comment on the prospect of facing favourite Rafa Nadal in the semis.
While Thiem's part in Djokovic's downfall should not be overlooked, it was the Serbian world number two's astonishing collapse that was the talk of Roland Garros.
Double French Open champion Jim Courier, commentating on the match, said the Serb had shown 'no fight'.
Images & Inputs: Reuters, AP