The Monte Carlo Masters 1000 produced major upsets on Monday as Argentine Sebastián Báez defeated three-time Grand Slam champion Stan Wawrinka in straight sets, while Francisco Cerundolo handed Stefanos Tsitsipas his first-ever opening-round defeat at the tournament . Báez, ranked 65th in the world, overcame a slow start to beat the 104th-ranked Wawrinka 7-5, 7-5 in one hour and 47 minutes, earning his first win in five appearances at the Monte Carlo Country Club . After falling behind 4-1 in the first set, the Argentine grew considerably into the match and became the main protagonist, taking a hard-fought opener before carrying those positive feelings into the second set where he built a comfortable 3-0 lead .
The victory was especially poignant as it marked Wawrinka’s final appearance at the tournament he won in 2014, with the Swiss player looking increasingly upset though still fully engaged throughout a second set that featured seven breaks of serve . Báez will now face an enormous challenge in the second round as he takes on world number one Carlos Alcaraz . The 24-year-old Argentine, who captured his fourth career title in Buenos Aires in February and reached the round of 16 at the Australian Open, is 15-6 on the year and has a chance to improve upon his career-high ranking of 18th .
In another significant upset, 16th seed Francisco Cerundolo locked up a 7-5, 6-4 victory over three-time Monte Carlo champion Stefanos Tsitsipas, handing the Greek his first opening-match loss in eight appearances at the tournament . Cerundolo recovered from letting a double-break lead slip in the second set to notch his first win in three meetings against Tsitsipas . The defeat will see Tsitsipas exit the top 60 in the ATP rankings for the first time since April 2018, when he stood at 63rd . The Greek had won 22 of 26 matches at Monte Carlo coming in but has struggled since opening the season, going 6-8 in tour-level tournaments thereafter .
Cerundolo, who took out Daniil Medvedev during the Miami Open, awaits Tomas Machac in the second round . The Argentine clay-court specialist has built on an impressive start to 2026 that saw him triumph in his birth city of Buenos Aires and reach the round of 16 at the Australian Open . With the early exits of Wawrinka and Tsitsipas, the Monte Carlo Masters has already delivered dramatic storylines as the European clay-court season heats up ahead of the French Open
