No. 5 seed Robin Haase and Mikhail Youzhny will complete their match on Tuesday.
The Latvian will meet Tatjana Maria, appearing in a WTA final for the first time.
Both received wild cards into the final Wimbledon tuneup.
Top seed Caroline Garcia and No. 7 seed Lucie Safarova fell on Friday.
Andreas Seppi also reached the final eight in Germany.
The No. 1 player in the world had to fend off two match points in the final set tiebreaker.
The French Open champion cited continued achilles pain and inflammation.
The Argentine could be forced from the game for up to six years.
No. 5 seed Carla Suarez Navarro and No. 8 seed Aryna Sabalenka also lost in Mallorca.
It is the Frenchman's 15th career title.
The Frenchman will face red-hot qualifier Bernard Tomic in the semifinals.
Top seed Adrian Mannarino, however, lost his opener in straight sets.
The rising Japanese star faced no break points and allowed only one service game to reach deuce.
Robin Haase and Yuichi Sugita also fell to lesser opponents.
No. 5 seed Stefanos Tsitsipas earned his maiden victory as a seeded player, while Bernanrd Tomic notched his first main draw tour win of 2018 in...
2017 runner-up Natalia Vikhlyantseva also lost her opener.
Magdalena Rybarikova and Alison Van Uytvanck also won, but Camila Giorgi fell.
The veteran German ran past Mikhail Youzhny in the first round.
The seven-time Wimbledon champion is said to be recovering nicely from a pectoral injury.
The defending US Open champion easily moved past Madison Keys to set up a championship match with Simona Halep.