Carlos Alcaraz of Spain celebrates to the crowd after his straight sets victory against Tommy Paul of the United States in their fourth round match at Hard Rock Stadium on March 28, 2023 in Miami Gardens, Florida. AFP
Alcaraz, the defending Miami champion and also the winner at Indian Wells earlier this month, will face another American in the last eight when he comes up against Taylor Fritz.
Paul came into the match having won his last 12 encounters with Spanish players, including wins over Alcaraz and Rafael Nadal last year, but he was unable to get a foothold in the contest.
It was the ninth straight victory for the 19-year-old Spaniard, who delighted a supportive South Florida crowd with his powerful strokes from the baseline and readiness to move forward, once again making use of his increasingly effective drop shot.
"I moved well and defended well and I counter-attacked and I think if I play at that same level I will have a lot of chances to get through," said Alcaraz.
"I feel at home here. It is easy to play here in Miami with all the energy I receive every day."
Tsitsipas had to wait a week for his first contest in Miami, beating Chilean Cristian Garin on Monday, but he came unstuck against Khachanov, losing 7-6 (7/4), 6-4.
The Greek has been troubled by a shoulder injury in recent weeks but Khachanov ended his six match losing streak against Tsitsipas and 23 match barren spell against top ten opponents.
His serve was reliable throughout and broke Tsitsipas’ serve to love in the fifth game of the second set and kept his cool to see out the win.
"Both of us were serving pretty well in the first set… Then I took it to the tie-break, and in the second set as soon as the opportunity came, I had to take it," he said.
In a clash of top-10 players, American Fritz defeated Denmark's Holger Rune 6-3, 6-4 to reach to the last eight in Miami for the first time in his career.
Fritz, who won at Delray Beach last month, beat Emilio Nava and Denis Shapovalov in straight sets before Tuesday's encounter and he was pleased with the way he was able to go on the attack.
"I couldn't play aggressively in my first two matches because my opponents were hitting every ball as hard as they could. (Rune) still crushes the ball but it was nice to feel I had some more time," Fritz said.
"The first two rounds, it was impossible to play my game, I just had to make balls. Today when I got the chance to be aggressive I was and I just wanted to serve well and try not to give him many free points."
- Eubanks ousts Mannarino -
Fritz will be joined in the quarter-finals by compatriot Christopher Eubanks who claimed another scalp by beating France's Adrian Mannarino 7-6 (7/2), 7-6 (7/5).
The game was delayed by rain for around four hours with Eubanks, ranked 119th in the world, 4-2 up in the first set and after play resumed Mannarino was able to force a tie-break before losing out to the big-serving American.
There was nothing to separate the pair in the second set but once again Eubanks triumphed in the tie-breaker to reach a Masters 1000 quarter-finals for the first time in his career.
Having come through the qualifiers in Miami, the 26-year-old Eubanks has won six straight game and will enter the top 100 in the world rankings for the first time.
Eubanks now faces world number five Daniil Medvedev after the Russian comfortably dealt with French qualifier Quentin Halys 6-4, 6-2 in a match which started after midnight following a four-hour rain delay.
Italian Jannik Sinner also advanced to the last eight without dropping a set and he was in firm control from the outset against Russian sixth seed Andrey Rublev, winning 6-2, 6-4.
Sinner, who has never failed to reach the quarters in his three appearances in Miami, will face Emil Ruusuvuori after the Finn beat Dutchman Botic van de Zandschulp 4-6, 6-4, 7-5.