World No.1 Novak Djokovic was upset Friday at the Geneva Open, losing 6-4, 0-6, 6-1 to Tomas Machac of the Czech Republic in the semifinals.

Machac, who was competing in his maiden ATP tour-level semifinal, showed his strength in the first set when he came back from 4-1 down to take it 6-4 for an early lead.

The Serbian put up the best answer in the second set with a 6-0 win and continued that momentum to go 1-0 up in the third set.

However, it's the Czech who had the last laugh as he won the next six games to end the roller-coaster match and advance into the final.

Djokovic, 37, struggled physically at times against his 23-year-old opponent and received a medical timeout at the end of the first set.

"I am looking forward to playing in a final for the first time," Machac said.

The other semifinal match between second-seeded Casper Ruud of Norway and Flavio Cobolli of Italy was suspended due to the rain.

In the double's, Marcelo Arevalo and Mate Pavic will face Lloyd Glasspool and Jean-Julien Rojer in the final after winning their respective semis.