Matteo Berrettini, of Italy, reacts after defeating Alejandro Davidovich Fokina, of Spain, during the fourth round of the US Open tennis championships, Sept 4, 2022, in New York. (JULIA NIKHINSON / AP)

NEW YORK - Italian Matteo Berrettini reached his second consecutive US Open quarter-final by winning a marathon battle with Alejandro Davidovich Fokina 3-6 7-6(2) 6-3 4-6 6-2 on Sunday after the Spaniard suffered an injury in the final set.

The 13th seed had lost to Davidovich Fokina on clay in Monte Carlo last year but found the right formula on New York's hard courts, sending down 17 aces, firing 48 winners to 27 from his opponent and saving nine of 13 break points.

After a lacklustre first set in which Matteo Berrettini produced only six winners and failed to earn a break point, Italy's Australian Open semi-finalist came to life in the second set tiebreak and immediately broke his opponent Alejandro Davidovich Fokina in the third set

After a lacklustre first set in which Berrettini produced only six winners and failed to earn a break point, Italy's Australian Open semi-finalist came to life in the second set tiebreak and immediately broke his opponent in the third set.

Down a break in the final set, Davidovich Fokina suffered an injury in the sixth game when his leg slipped out from under him and he banged his fists on the court in pain.

He saw a physio and for a moment it seemed he might be done for the day but the Spaniard bravely returned to the court to finish the match to roars of encouragement from the crowd.

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"I'm really proud because I didn't start the match the way I wanted to," said Berrettini, who has been sidelined a number of times this season due to injuries or illness.

"Obviously this is not the way I wanted to finish the match but I'm going to take the win."

He next faces Norwegian fifth seed Casper Ruud, who ended lucky loser Corentin Moutet's fairytale run 6-1 6-2 6-7(4) 6-2 to kick off the action at Arthur Ashe Stadium.

Alejandro Davidovich Fokina, of Spain, returns to Matteo Berrettini, of Italy, during the fourth round of the US Open tennis championships, Sept 4, 2022, in New York. (JULIA NIKHINSON / AP)

Frenchman Moutet made history on Friday when he became the first lucky loser to reach the U.S. Open fourth round and put up a valiant defensive effort to save 10 of 17 break points.

But Ruud, the runner-up at Roland Garros this year, had the edge as he won nearly three-quarters of his first-serve points and hit 43 winners.

Ruud leads Berrettini 3-2 head-to-head, most recently beating him in the Gstaad final, but is not taking his opponent lightly.

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"He's dangerous obviously on all surfaces," the Norwegian told reporters. "He will throw big serves, big forehands. He has big weapons... It's going to be a tough challenge, for sure."