Novak Djokovic's wait for a 100th ATP singles title continues after he exited the Monte Carlo Masters in a "horrible" straight-set opening loss to Alejandro Tabilo.
Djokovic, a two-time winner of the event, made 29 unforced errors compared to his 18 winners in a subdued start to the 37-year-old's clay-court season, resulting in a 6-3 6-4 defeat.
The record 24-time men's major champion had won the last 10 matches he had contested on clay - including his run to Olympic gold in July.
But Chilean Tabilo, who beat Djokovic on the surface at the Italian Open 11 months ago, replicated that surprise victory to reach the third round.
On Wednesday, Carlos Alcaraz rallied to a comeback victory over Francisco Cerundolo in the 21-year-old's first clay match of the season.
Spanish world number three Alcaraz was unable to match Argentine Cerundolo in the first set but dominated thereafter, winning 12 of the last 13 games for a 3-6 6-0 6-1 victory.
Norwegian fourth seed Casper Ruud beat Spain's Roberto Bautista Agut 6-2 6-1 to reach the third round, while Russian seventh seed Andrey Rublev overcame Frenchman Gael Monfils 6-4 7-6 (7-2).
Australian eighth seed Alex de Minaur came from behind to defeat Czech Tomas Machac, while Russian ninth seed Daniil Medvedev beat Alexandre Muller of France, also in three sets.