Carlos Alcaraz, 18, youngest man in US Open quarterfinals since 1963

Botic van de Zandschulp upsets Diego Schwartzman in epic 5-set match (0:40)

Botic van de Zandschulp beats Diego Schwartzman in a five-set match for the ages to earn a spot in the quarterfinals. (0:40)

NEW YORK -- Carlos Alcaraz became the youngest man to reach the quarterfinals of the US Open since 1963 on Sunday.

The 18-year-old from Spain reached the final eight at Flushing Meadows by beating 141st-ranked qualifier Peter Gojowczyk of Germany 5-7, 6-1, 5-7, 6-2, 6-0.

Alcaraz now plays No. 12 seed Felix Auger-Aliassime, a 21-year-old from Canada who reached his second straight major quarterfinal by defeating Frances Tiafoe of the U.S. 4-6, 6-2, 7-6 (6), 6-4 with the help of 24 aces.

"At some point, age is just a number,'' Auger-Aliassime when asked about Alcaraz. "He already feels like a player that is established."

The 55th-ranked Alcaraz got past No. 3 Stefanos Tsitsipas in his previous match and is the youngest player with two five-set Grand Slam wins in a row since Michael Chang was 16 at the 1988 U.S. Open.

Auger-Aliassime had never reached the final eight at any Grand Slam tournament until Wimbledon in July, a month before he turned 21 on Aug. 8. Now the Canadian is the youngest man to reach consecutive major quarterfinals since Juan Martin del Potro made it to three straight in 2008-09.

Botic van de Zandschulp made history as well on Sunday.

He was playing in Louis Armstrong Stadium for the first time for his 4 hour, 20 minute, will-he-or-won't-he-blow-it victory, an incredible enough achievement for the Dutch qualifier.

Throw in this: Van de Zandschulp had never set foot in the United States before he arrived for the US Open.

Now, van de Zandschulp has another first of epic proportions: He's in the quarterfinals at Flushing Meadows -- just the third male qualifier to get that far in the Open era.

"I think before the tournament, no one expected me to reach the quarterfinals here," he said.

Van de Zandschulp continued his out-of-nowhere run, beating No. 11 Diego Schwartzman 6-3, 6-4, 5-7, 5-7, 6-1 on Sunday.

Van de Zandschulp was part of a trio of US Open qualifiers that reached the fourth round for the first time since the tournament began keeping qualifying records in 1982. He joined Nicolas Escude (1999) and Gilles Muller (2008) as just the third men's qualifier to reach the quarterfinals since the Open era began in 1968.

Before the US Open, the ninth-year pro had only five tour-level wins, was never ranked higher than 117 in the world and had never advanced past the second round in a Grand Slam tournament.

"His tactic today was working perfectly," Schwartzman said. "Maybe I had luck in the third and fourth to continue playing the match today because he was playing better than me."

His next match is against No. 2 Daniil Medvedev, who cruised into the U.S. Open quarterfinals with a 6-3, 6-4, 6-3 win over Daniel Evans on Sunday.

Medvedev has yet to drop a set on his way to the quarterfinals for the third straight year, and van de Zandschulp would be the third unseeded player he would face at Flushing Meadows. Evans was No. 24.

"When I'm playing against guys who are better than me or better in general, my level is also increasing," van de Zandschulp said. "I prefer to play against better guys."

The 25-year-old van de Zandschulp had already knocked out No. 8 seed Casper Ruud in the second round. He also dropped the first set in each of his first three U.S. Open matches before reversing the trend against Schwartzman.

It has been a big season already for qualifiers. Russian Aslan Karatsev was a qualifier when he reached this year's Australian Open semifinals.

The signs, though, were apparent that van de Zandschulp could surprise in Slams. He went 11-1 in Grand Slam qualifying this year. He made the main draw at Wimbledon as a lucky loser -- getting into the bracket when someone else withdrew -- and reached the second round.

"I knew that I could beat players who are ranked 20 or 10 in the world," he said. "But I didn't do it like this often, this consistently. I think I'm playing really consistently here, showing some good tennis throughout the whole tournament. So, yeah, that's new for me."

The Associated Press contributed to this report.