It is a wild semifinal lineup at the Rio Open, where zero players in the top 30 have advanced at this ATP 500 tournament only one inside the top 59 is still in contention for the title. Taking the court on Saturday will be world No. 31 Sebastian Baez, No. 60 Alexandre Muller, No. 86 Francisco Comesana, and No. 91 Camilo Ugo Carabelli.

The second semifinal between Muller and Comesana–which marks their first head-to-head encounter–is a showdown between two guys who aren’t very well known but have taken Rio de Janeiro by storm.

Muller has unquestionably been the most impressive player in the entire draw. The 60th-ranked Frenchman silenced the Brazilian crowd by beating Buenos Aires champion Joao Fonseca in the first round and then dismissed eighth seed Tomas Martin Etcheverry and fourth seed Francisco Cerundolo. Three-set marathons have mostly been the norm this week, but Muller has not dropped a single set. The 28-year-old is now 8-2 for the 2025 campaign with his first ATP title in Hong Kong.

Coming into this week, Comesana had twice as many match wins at Grand Slams (four) as he did on the entire rest of the ATP Tour (two). The 24-year-old Argentine has picked up three more in Rio, beating Gustavo Heide 7-6(2), 6-7(7), 6-3, Nicolas Jarry 7-6(4), 6-7(1), 7-6(6), and top seed Alexander Zverev 4-6, 6-3, 6-4. Comesana has spent a ridiculous nine hours and six minutes on the court through three rounds.

Fatigue has to become a factor at some point. Moreover, Comesana has never been on this kind of stage–whereas Muller just picked up an ATP title last month. The world No. 86 almost certainly won’t go down without a fight, but Muller should be able to outlast him.

Pick: Muller in 3