Carlos Alcaraz kept alive his bid for a first Grand Slam title after coming through a remarkable <a href="https://www.thenationalnews.com/tags/us-open" target="_blank">US Open</a> quarter-final against fellow rising star Jannik Sinner on Wednesday night. Alcaraz, seeded third and one of the pre-tournament favourites in New York, demonstrated precisely why he is regarded as the future of men's tennis with a 6-3, 6-7, 6-7, 7-5, 6-3 victory over Italian 11th seed Sinner. It earned the 19-year-old Spaniard a measure of revenge after losing to Sinner, 21, in their previous two encounters this year, but he was on the brink of a third successive defeat and needed to save match point in the fourth set. After another enthralling encounter between these two talented youngsters, an exciting on-court rivalry is developing, which suggests men's tennis should be in safe hands in the post-Big Three era when Novak Djokovic, Rafael Nadal, and Roger Federer ultimately hang up their racquets. "Honestly, I still don't know I did it," said Alcaraz, who will face Frances Tiafoe in the semi-finals after the American enjoyed a comparative breeze in his straight-sets win over Andrey Rublev. "It was a high quality and unbelievable match. Jannik is a great player. His level is just amazing. "I always say that you have to believe in yourself all the time. Hope is the last thing that you lose. I just believed in myself and believed in my game." The 5hr 15min duel finished at 2.50am local time, making it the latest ever finish in the tournament's 141-year history. The previous record for the latest finish to a US Open match was 2.26am, which had been set three times before. But for the few thousand spectators who stuck it out inside Arthur Ashe Stadium, it was worth every minute of staying up past their bed times. It was a contest full of high quality shot-making and relentless momentum swings, starting with Alcaraz taking the immediate initiative with a break in the first game of the match. His advantage didn't last long, though, as Sinner broke back for 2-2 and held for his first lead at 3-2. That seemed to jolt Alcaraz into finding a new gear as the world No 4 stormed through the next four games to take the first set. Any suggestion that could set up a comfortable win for the two-time Masters champion were swiftly extinguished when Sinner claimed the first break of the second set to lead 2-1, an advantage he held until serving for the set at 5-4 when Alcaraz pounced on his only chance to level. A tense tiebreak soon followed, with both players saving a break point each before Sinner converted his second opportunity to level a match that was shaping up to be a classic. The momentum then swung back towards Alcaraz when he broke and held for 4-2 in the third set, but a loose service game saw Sinner strike back for 4-4. Once again, the set went to a tiebreak and Sinner sprinted into a 6-0 lead before taking the set when an Alcaraz return drifted long. Sinner carried his momentum into the fourth set with an early break and looked to be in control after holding to take a 3-1 lead. But Alcaraz again staged another fightback and after holding serve, broke Sinner to level at 3-3 with a blistering forehand down the line. Yet the Spaniard's grit in restoring parity went out the window when Sinner broke back immediately, Alcaraz double-faulting on break point to gift his opponent a break and a 4-3 lead. That led to Sinner serving for the match at 5-4, and it appeared as if a thrilling duel was about to reach its conclusion when the Italian moved to match point. But Alcaraz clawed it back to deuce with a backhand return before Sinner then double-faulted to cough up a break point. On the next point Sinner lashed a forehand way wide to leave the score at 5-5. Alcaraz then held and broke to force the fifth set decider. Still there was more drama in store in the fifth, with Sinner going a break up. But Alcaraz would not be denied, hitting back with two breaks to set up a remarkable win. It was the second early-hours-of-the-morning finish this week for Alcaraz, who had edged past Croatia's Marin Cilic in another five-set epic in the fourth round in a match that finished at 2.23am local time on Tuesday.