Rafael Nadal's memories of his lone match against Borna Coric are a bit fuzzy, which is understandable.
When the two met in the Swiss Indoors last October, Nadal had just decided to undergo season-ending appendix surgery once his run in the tournament ended. That would come against Coric, a gifted teen from Croatia who won that day in straight sets against a sluggish Nadal.
''It was a tough moment of the year for me,'' the 14-time Grand Slam champion recalled Saturday.
''I don't remember it very well, but I think I played very bad,'' Nadal added, laughing.
The two men face off for the second time Monday, and for good reason, U.S. Open organizers believe it could be a compelling match. It closes out the night session at Arthur Ashe Stadium as the year's final Grand Slam tournament begins.
Coric just missed out on a seed with a ranking of 35th, making the 18-year-old a particularly difficult first-round matchup for a top player.
''He's one of the players that is the future of our sport, so it's a tough one,'' Nadal said. ''But I'm playing well.''
That Nadal would need to insist he is in good form is telling. The appendix surgery was just the latest health problem at the time for Nadal, who was unable to defend his U.S. Open title last year because of a right wrist injury.
The 29-year-old Spaniard is seeded just eighth and was upset in the second round at Wimbledon by 102nd-ranked qualifier Dustin Brown. This month, Nadal failed to make it past the quarterfinals in two hard-court warmups.
But he keeps saying he is now playing better than those results show, and he'll get a chance to prove that right away against an opponent of Coric's caliber.
Some other things to watch as the U.S. Open begins:
SERENA STARTS SEEKING SLAM: Three-time defending champion Serena Williams plays the first match of the night session on Ashe, seeking the first of the seven victories she'll need to complete the first Grand Slam since Steff Graf in 1988. The top-ranked American carries a 21-match U.S. Open winning streak - and 28-match major winning streak - into her meeting with Vitalia Diatchenko.
The 86th-ranked Russian is 2-6 in Grand Slam matches, with both victories coming on clay at the French Open. The first was way back in 2009, when she faced then-No. 1 Dinara Safina in the second round -and lost 6-1, 6-1.
Venus Williams plays on Ashe earlier in the day, facing Monica Puig.
MARIA MISSING: No. 38-ranked Daria Gavrilova, making her U.S. Open main-draw debut, now has a very different first-round matchup. She was originally supposed to face five-time major champion Maria Sharapova on Monday. But after the third-seeded Sharapova withdrew Sunday because of a lingering right leg injury, Gavrilova will meet another Daria from Russia: 133rd-ranked ''lucky loser'' Daria Kasatkina. Fan favorite Gael Monfils' opening match was moved to Louis Armstrong Stadium, the Open's second-largest venue, to replace Sharapova's.
NO ASHE FOR CILIC: For the first time since 2001, the reigning men's champion won't open the defense of his U.S. Open title on Ashe. Marin Cilic, last year's surprise winner, faces 91st-ranked Guido Pella of Argentina on Armstrong. Cilic is seeded ninth after an injury-plagued season.
At Wimbledon, the reigning men's champ has the honor of playing the tournament's first match on Centre Court. While there isn't a similar formal tradition at the U.S. Open, Cilic's placement is unusual. Marat Safin, the 2000 champ, was the last who didn't open his defense on Ashe.
Playing before Cilic on Armstrong is the man he beat in last year's final, Kei Nishikori. The fourth-seeded Nishikori said Saturday that he had no lingering issues with the hip injury that forced him to pull out of the hard-court warmup at Cincinnati.
Top-ranked Novak Djokovic and Nadal are the two seeded men to play on Ashe on Monday.
FISH'S FAREWELL: American Mardy Fish's career will end with the U.S. Open, but he may be able to stick around for a bit. He got a favorable first-round matchup against 102nd-ranked Marco Cecchinato of Italy, who is making his Grand Slam debut and is 0-6 in tour-level matches. The 32-year-old Fish was once ranked in the top 10 but had his career derailed by struggles with anxiety disorder. He plays the day's first match on the Grandstand.
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