New York - Five talking points for the US Open, the final Grand Slam of the season which gets under way at Flushing Meadows on Monday:
Rafael Nadal and Roger Federer have 37 Grand Slam titles between them and have clashed 38 times in a mesmerising rivalry stretching back to 2004.
However, the world's two top players have never met at the US Open.
Nadal leads their head-to-head 23-15 and is 9-3 at the Slams. Nine of those 12 at the majors have been in finals with the pair never having met before the semi-finals.
If they are to meet at the US Open this year, it can only be in the final as Nadal is top seed and Federer is seeded two.
Federer has won five US Open titles, but they all came between 2004-2008. He has even been French Open champion (2009) since the last time he triumphed in New York!
Since 2008, he has twice been a runner-up - to Juan Martin del Potro in 2009 and Novak Djokovic in 2015.
Del Potro returned to haunt him again last year when the towering Argentine triumphed in the quarter-finals.
Now 37, Federer would become the oldest New York champion in the Open era should he lift the trophy again on September 9 and second oldest of all time.
"It's even a bigger priority this year, the US Open, than it has been last year. Not that it wasn't last year, but Wimbledon was key for me last year," Federer said Friday.
They are young, gifted but not quite yet the finished product. Tennis's widely-touted 'NextGen' are still to make an impact at the Slams with much expected of German star Alexander Zverev, the world number four.
The 21-year-old has yet to get past the quarter-final of a Slam while his last two visits to New York have seen second-round exits.
Greek player Stefanos Tsitsipas, 20, who is ranked 15 having been at 161 in the world this time last year, made his mark at the Toronto Masters this month where he defeated Zverev, Novak Djokovic and Kevin Anderson on his way to the final where he lost to Nadal.
"Zverev's been struggling at Slams maybe a little bit, sure, but he's still young, so time is on his side," said Federer of a player who has hired Ivan Lendl as his coach.
Serena Williams missed the US Open last year as she prepared to give birth to daughter Olympia. Her return to the sport has been a rollercoaster with a runners-up spot at Wimbledon followed by a 6-1, 6-0 defeat by Britain's Johanna Konta in San Jose - the worst loss of her career.
However, the 36-year-old is still one of the favourites to lift a modern era record seventh US Open and 24th career Grand Slam to go level with the mark set by Margaret Court.
"I think the surface plays in her favour, as does competing at her home Grand Slam and having an American crowd cheer for her. All of those things will be helpful," former champion Martina Navratilova told wtatennis.com.
"It's about trying to win a 24th Grand Slam to equal Court - that's the number she cares about."
When Andy Murray won the US Open in 2012, he ended Britain's 76-year wait for a men's singles champion at the Slams. He has gone on to add two Wimbledons to his CV, but his career has been stalled by hip surgery in January which has seen his ranking slump to 378 in the world.
The 31-year-old has not played at a Slam since Wimbledon in 2017 and there remain serious doubts over whether or not he can last two weeks of intense best-of-five sets in New York.
"It feels slightly different, this one, because for the last 10 years or so I've been coming and trying to prepare to win the event, whereas I don't feel like that's realistic for me this year," he admits.