Daniel Altmaier failed to convert nine of his 10 break opportunities as Carlos Alcaraz reached the quarter-finals in Monte-Carlo.
Carlos Alcaraz reached the Monte-Carlo Masters quarter-finals with a 6-3 6-1 victory over Daniel Altmaier, as his return game did the work.
Alcaraz's quest for a maiden title in Monte-Carlo could have been derailed by a below-par serving performance, as he was forced to save 10 break points throughout the contest.
Five of those came in Alcaraz's very first service game, as he held off some determined play from Altmaier, ranked 84th in the world.
When Alcaraz got his first break five games in, two more followed in succession to hand him the opening set.
The second set would follow a similar pattern. Alcaraz had to fend off three more break points for Altmaier in the opening game, but he found his groove with a five-game winning streak that carried him home.
The Spaniard said in his courtside interview: "Honestly, it was difficult, Danny is playing great.
"He's a solid clay-court player with a difficult game: A lot of topspin shots and really good physically. The score doesn't show how difficult it was… I had to battle in the first set.
"It was good to get a break before the new balls, which helped with the serve. In the second set, I could be myself, play more aggressively than in the first, and I took my chances."
Next up for Alcaraz is Arthur Fils, who is the youngest player to make the quarter-finals at all of the first three ATP Masters 1000 events of a single season since the format's introduction in 1990.
Alcaraz is not the only Spaniard into the last eight, after Alejandro Davidovich Fokina registered an impressive 6-3 6-7 (6-8) 6-4 victory over Jack Draper.
In the last five years, only Stefanos Tsitsipas (four before his own last-16 match later on Thursday) has made more quarter-finals at the Monte-Carlo Masters than Davidovich Fokina (three, equalling Jannik Sinner).
But there will be no deep run for Casper Ruud, who lost 6-4 3-6 7-5 to Alexei Popyrin.
Popyrin, whose four matches so far have all gone the distance, has now been responsible for two of the three top-10 victories by Australian players at the Monte-Carlo Masters, having also beaten Andrey Rublev last year.
Data debrief: Alcaraz into last eight again
Alcaraz keeps collecting quarter-final spots at the biggest events in tennis.
He has now made the last eight at 12 of the 13 ATP Masters 1000 or grand slam events he has taken part in, with the Italian Open in Rome being the only exception.
The 21-year-old now has 83 clay-court wins to his name from 101 matches on the surface.