The Spaniard suffered a first-week exit from Wimbledon for the second successive year as Darcis - the world number 135 who has not won a tournament since 2008 - prevailed in three straight sets, 7-6 (7/4) 7-6 (10/8) 6-4.
It was a loss no-one saw coming, with Darcis - the lowest-ranked player Nadal has lost to since he went down to the 690th-rated Joachim Johansson in 2006 - priced at 100/1 with some bookmakers.
Form and reputation counted for nothing, though, just as it did not against Lukas Rosol last year. That day Nadal was clearly suffering with his long-standing knee problem which would then sideline him for seven months. As he struggled to move his taped-up left leg on Monday, there were ominous shades of a repetition.
The 12-time major champion would not enter into talk about a recurrence, though, batting away repeated attempts to snare an excuse from him.
"That is sport, sometimes you play well and you have the chance to win, sometimes you play worse and you lose, that's the good thing about the sport," said the 27-year-old.
"For me, there were not a lot of things good, but I congratulate Darcis who played well. This is not the right day (to talk about injury). I tried my best in every moment, but this was not right for me."
Nadal was advised to miss his traditional grass-court warm-up in Halle by his doctor and arrived in London short on practice on the surface.
Known as the 'King of Clay', his recent eighth win at the French Open was not a surprise, but with him required to get lower to play the ball on grass, thus putting further strain on his joints, a lack of game time on grass was evident.
"I didn't have the chance to play in Halle. I cannot go back," he said.
"I tried my best and congratulate the opponent. It is not a tragedy, it is sport."
A tragedy it may not be, but it ranks as one of the greatest shocks of recent times. Darcis is one of the tour's lesser-known players and has never gone beyond the third round of a slam.
With all that considered, it was assumed Nadal must have been injured, but he steadfastly refused to admit if he was as the questioning continued.
"I think you are joking because I will not talk about my knee this afternoon," he added.
"All I can say is congratulations to Steve. Anything I say about my knee is an excuse and he does not deserve an excuse."
When Nadal bowed out to Rosol he was not seen again for seven months. He said he would not be "that long" again, and chose to reflect on his comeback as a whole, rather than this loss in isolation.
With seven titles including his record-breaking Roland Garros success, he claimed to have surpassed anything he thought possible.
"I played much more than I dreamed before here after the injury, so that's a fantastic and very positive thing for me," he said.
"I won seven tournaments out of nine and I am happy with everything. Losses can happen."