Defending U.S. Open champion Rafael Nadal advanced to the quarterfinals Sunday with a four-set win over Georgian Nikoloz Basilashvili, 6-3 6-3 6-7 (6) 6-4.

The world No. 1 staved off an impressive comeback by Basilashvili, who valiantly took the third set in a tie-breaker. But Nadal would not be denied, outlasting the 26-year-old in a three hour, 18-minute match.

Nadal appeared particularly energized in the Round-of-16 match at Flushing Meadows. When he delivered an ace on triple-match point, the Spaniard excitedly pumped his fists. After shaking hands, Nadal immediately returned to the court and lifted his arms in triumph.

The Spaniard later admitted that he was "very happy to be through."

The win for Nadal comes on the heels of a tight, four-hour 23-minute victory over Russian Karen Khachanov in the third round.

"Two matches in the row that were very tough ones,” said Nadal, who had seven aces against Basilashvili.

Nadal credited Basilashvili, who will soon be ranked in the top 30, for playing aggressively. Basilashvili finished with 56 winners, while Nadal had 30.

“He played fantastic," Nadal said of Basilashvili. "A lot of credit to him. He was playing great, hitting the ball very, very strong."

Things don't get any easier for the three-time U.S. Open champion. Up next for Nadal is a French Open final rematch against No. 9 seed Dominic Thiem. The Austrian star advanced with a Round-of-16 win over last year's finalist Kevin Anderson, 7-5 6-2 7-6 (2).

Rafael Nadal celebrates a win in his men's singles fourth round match against Nikoloz Basilashvili at the 2018 US Open. Elsa/Getty Images