Carlos Alcaraz admitted Ben Shelton was driving him "mad" before dispatching the big-serving American to continue his march towards back-to-back French Open titles.
The Spaniard dropped the third set but still collected his 100th Tour level clay-court win, 7-6 (8) 6-3 4-6 6-4.
"Honestly, today I fought against myself in the mind. I just tried to calm myself - in some moments I was mad," he said.
"I was angry with myself, talking not good things. I'm happy that I didn't let that thought play against me.
"I tried to calm myself and tried to keep going. That's what I tried.
"Every time we face each other we bring the level to the top. We entertained the people. He is a really powerful player. He can make any shots.
"I think we played really great tennis. Drops, coming to the net, big shots, and we stayed there in the whole match. For me, it is great having Ben around, a great energy for tennis and for the people. I love watching him play."
Alcaraz will face another American, 12th seed Tommy Paul, in the quarter-final.
Paul ended the hopes of Australia in the men's draw with a 6-3 6-3 6-3 win against Alexei Popyrin.
Frances Tiafoe joined his fellow American in the last-eight with a straight-sets victory over Daniel Altmaier.
The 15th seed had never previously made it beyond the third round at Roland Garros, but he will face Lorenzo Musetti or Holger Rune for a place in the semi-finals.
