NEW YORK: The U.S. Open is on track for a record number of five-set matches in the men's draw and American Frances Tiafoe says Roger Federer and Rafa Nadal have a lot to do with that -- even though they are not even playing at Flushing Meadows this year.

World number one Novak Djokovic is the sole representative of the 'Big Three' of men's tennis, with Federer and Nadal ruled out due to injury.

With 11 matches still to go in the men's draw, this year's tournament has already seen 33 matches reach a fifth set, the most at the hardcourt major since 2004 when 34 matches went to five.

Tiafoe, who lost to Felix Auger-Aliassime on Sunday, said players saw the absence of Federer and Nadal as an opportunity to go deep into the tournament.

"I definitely think guys are trying extra hard, because there is no Roger, Rafa," the 23-year-old American told reporters.

"I see guys foaming in the mouth, pretty funny to watch, I'm in the locker room cracking up.

"You have (Andreas) Seppi, like 37, playing 15-13 in the fifth (set tiebreaker). What's that about? Crazy.

"His 19th U.S. Open, he's putting his heart on the line. He's probably not doing that if he plays Rafa the second round, probably, like, 'I'm done'.

"It's unreal."

This year's tournament is already tied with the 1980 and 1983 editions with seven fifth-set tiebreakers, the most since the U.S. Open started using tiebreaks in 1970.

As many as 10 players have come back to win after losing the first two sets, also tied for the most with the 1974 and 2012 tournaments.

"Coming in this U.S. Open we knew it was going to be intense. We knew there was going to be lots at stake," said Auger-Aliassime.

"On the one hand we have Novak trying to achieve history and we have guys that now have multiple Grand Slam finals ... all these guys that are really hungry, and myself, to be in the big stage and to win these type of tournaments."