Rafael Nadal captured his 16th-ever Grand Slam title on Sunday. (Photo: Getty Images)
Rafael Nadal won his 16th Grand Slam championship on Sunday at the US Open.
On Saturday, Sloane Stephens captured the first major title of her career at the Open.
Nadal was expected by many to win his third US Open and the fact that he did -- beating South Africa's Kevin Anderson, 6-4, 6-3, 6-4 -- reflected what kind of year 2017 has been in men's tennis at the highest levels. In a resurgent year for legends, Nadal and Roger Federer, arguably the two greatest players in the history of the men's game, won all four major tournaments, splitting them at two apiece.
The victory by the unseeded Stephens -- who easily defeated fellow American Madison Keys, 6-3, 6-0 -- was a bit of a surprise in a year of surprises for the women. With Serena Williams on maternity leave after winning the Australian Open in January, four different women won the Grand Slams this year: Williams (Australian), Jelena Ostapenko (French Open), Garbine Muguruza (Wimbledon) and Stephens (US Open).
Here are five questions going forward for tennis in 2018.
1--When will Serena come back?
Williams gave birth to a baby girl during the first Friday of the Open and won't play for the rest of 2018. When will she return and can she return to dominance when she does? Williams could come back in January to defend her Australian Open title...or she could wait until the spring hardcourt season....or she could return at the French Open. Whatever happens, don't rule out Williams adding to her total of 23 Grand Slam titles, the most in the Open Era.
"I love it when people say that there's no chance of Serena coming back," her coach, Patrick Mouratoglou, told Vanity Fair earlier this year. That's the best thing that the media can do, so I say to all journalists and commentators: 'Please, go for it.' If she comes back, she will do everything in her power to win Grand Slams again. She won't play again if she thinks she couldn't win Grand Slams again." 
2--What's ahead for Roger Federer?
Federer, 36, is nearing the end of his legendary career, but when exactly that ending will come is anybody's guess. He returned after a six-month layoff following Wimbledon in 2016 to win two major tournaments this year at the Australian Open and Wimbledon, skipping the French Open in between. He has won five tournaments so far, and plans to continue playing this fall and winter. Odds are he plays a limited schedule again in 2018, saving himself for the big events.
"Now I have Laver Cup, Shanghai, Basel, Paris, and London," he said after losing to Juan Martin del Potro in the quarterfinals. "That's my schedule, and it won't change. I hope I'm fully recovered and 100 percent fit when Laver Cup comes around. When that's over, I hope I'm going to arrive really early in Shanghai to really get ready and make it a priority for me to win that tournament. So that's the schedule there."
3--What can we expect from Novak Djokovic and Andy Murray?
Djokovic (shoulder) and Murray (hip) both missed the Open with injuries and aren't expected to play for some time. Meantime, they can look to Federer for inspiration. After taking six months off in 2016, Federer returned fresh and had a brilliant first half of 2017. Djokovic (12 majors) and Murray (3) must hope that similar rest will propel them toward more majors titles in 2018 and beyond.
"Look, I want to be back on court as soon as I can," Murray said when he withdrew. "If it means that I can play before the end of the year, then, you know, that's what I would love to do. I miss competing, and I'll try to get myself back on court as soon as I can."
4--Are the American women poised to dominate?
For the first time since 1981, four American women closed out the semifinals of their home Slam, with Stephens, 24, ultimately prevailing over Keys, 22. Venus Williams and CoCo Vandeweghe also made it to the women's semis. Venus, 37, had a brilliant year late in her career, reaching two Grand Slam finals and one semifinal. With young players like Stephens, Keys, Vandeweghe all in their 20s, American women not named Williams should look forward to multiple Slams going forward.
"Winning a tournament is extremely special, but winning the US Open, being an American player, is even more incredible," said Stephens, who became the first American woman not named Williams to win a major since Jennifer Capriati at the 2002 Australian Open.
5--What young American man is in the best position to challenge for a major?
While the American women ruled the US Open, Sam Querrey, 31, was the only American man to reach the quarters, becoming the first to do so at his home Slam since John Isner in 2011. Querrey also reached the semis at Wimbledon, but he's hardly considered young blood. Other young Americans, like Jack Sock, Ryan Harrison and Jared Donaldson, went out early at the Open, leaving Andy Roddick in 2003 as the last American man to win a major.