Spanish young gun Carlos Alcaraz showed the door to 39-year-old compatriot Feliciano Lopez with a 4-6, 6-2, 6-4 comeback performance on the home clay of Marbella on Thursday.
The 17-year-old winner reached the quarter-final for the first time at the ATP level.
Victory in two hours puts Alcaraz into the last eight against Norway’s Casper Ruud, who defeated Italian Gianluca Mager 6-3, 6-2.
The Alcaraz-Lopez clash was the biggest age difference between two players since 2011 Vienna, when Dominic Thiem, 18, beat 44-year-old Austrian countryman Thomas Musters.
The young winner put over seven aces and broke Madrid Masters TD Lopez five times.
Spain’s 95th-ranked Jaume Munar beat Monte Carlo champion Fabio Fognini 6-2, 6-1 for a first victory over a Top 20 player this season.
The 23-year-old needed 94 minutes and six breaks of the Fognini served form 16 chances to go through.
Munar now plays for the semis against Ilya Ivashka, who beat Spanish fifth seed Alejandro Davidovich Fokina, 6-1, 6-3.