Andy Murray suffered another early ATP Tour exit on clay as Italy's Fabio Fognini came up trumps in their first-round battle after two hours and 54 minutes.
Fresh from ending a four-year title drought at the Aix-en-Provence in France, Murray threatened another of his classic comebacks after recovering from a set down to force a deciding third.
However, a torrid opening service game in the third set proved costly, as Fognini prevailed 6-4 4-6 6-4 to set up a second-round encounter with Miomir Kecmanovic.
The warning signs were there early on for Murray, who fell 40-0 down on serve in the opening game and faced five break points in total, but in typical fashion, he saved all of them to hold.
Fognini continued to dictate proceedings and would earn a deserved break in the third game, before beating away three break points of Murray's to clinch the first set.
A fired-up Murray came out all guns blazing in the second set, roaring into a 5-1 lead before Fognini pegged him back to 5-4, but the former world number one earned his fourth break of the set in the 10th game to stay alive in the match.
It was not to be for Murray, though, as Fognini broke his serve in the opening game of the third set and dropped a mere three points on serve henceforth to power into the second round.
The former British number one won just 35% of points behind his second serve and did not fashion a single opportunity to break Muller, who fired six aces en route to a comfortable victory in 62 minutes.
The pair traded respective holds in the opening two games before Muller went on the warpath, winning five games on the bounce to wrap up the first set with aplomb.
Despite holding in his opening two games of the second set, Edmund's resistance was soon ended by Muller, who broke in the fifth game and when Edmund was serving to stay in the match to cruise through to round two.