Wimbledon's done, so what now? Our biggest questions leading to US Open

LONDON -- From the jump, it was a wacky fortnight, with unprecedented upsets, marathon matches and a resurgence by some of the sport's greatest stars. Also: royals!

Although this Grand Slam is in the rearview, there is much tennis yet to be played this season. Here are five questions as we depart All England and prepare for the hard-court swing.

Will Serena win another Slam?

This is the question after every match Serena Williams has contested since returning from maternity leave in March (all 14 of them). Where does she believe she is in her comeback? Fifty percent of Serena-at-her-best Serena? Seventy-five percent? Can you put a percentage on it for us, please?!

If Williams did anything over the past two weeks, it was bury the question of whether she will be able to return to the level she was at before she announced to the world that she was pregnant, even if she hasn't arrived there yet. Her power is there; so, too, is her serve, which topped out at 125 mph in the final against Angelique Kerber. Williams also showed much-improved footwork, speed and overall fitness. She also went into the women's final carrying something just as important: the belief that she could win. At some point, everyone else started to believe, too.

"To hear people say, 'Oh, she's a favorite,'" Williams said after her semifinal win. "Like, the last 16 months, I've played in four tournaments and was carrying another human for half that time. It's like, 'C'mon, guys, this is pretty awesome.'"

It's safe to say that after experiencing only the seventh Grand Slam final loss of her career, Williams is more motivated than ever to reach another major final, tick off those No. 24 and No. 25 Slams and ditch that Open era asterisk. That, too, would be awesome.

Will Andy Murray return to tennis?

After testing his surgically repaired right hip in two warm-up events on grass, Murray withdrew from Wimbledon on the eve of the tournament. Working instead as a commentator for the BBC as he continues to recover, he said skipping his home Slam and delaying his return to best-of-five, no-tiebreak tennis was "the smart thing to do."

Murray has played in only three tournaments since he reached last year's Wimbledon quarterfinals, but he plans to begin his hard-court bid at the Citi Open in Washington, D.C., at the end of the month. With the US Open looming, the 2012 champ said hard courts provide his best opportunity for a safe return. (He last played on the surface in New York in 2016.)

"As soon as I got on the hard courts, I felt better due to the stability of the surface," Murray said. "On grass, you are worried about every step you take. On the hard courts, I felt more comfortable. The impact on the hard courts is greater than the grass, but I feel it'll be a positive for me."

What is going on with Sloane Stephens?

For the second straight year, the top-ranked American woman was shown the Wimbledon exit in the first round. Since winning her first major at the US Open this past September, Stephens has either made the final (2018 French) or lost in the first round (Australian, Wimbledon) of the other Slams. Her year, like her career, has been a landscape of peaks and valleys. When she wants it, Stephens can find the fire to beat the best players in the world. What she hasn't shown is the ability to play consistently great tennis.

"We play a very long season," Stephens said after her first-round loss against unseeded Donna Vekic at Wimbledon. "There's no one that is going to win every single week. Even the No. 1 player in the world loses. Sometimes people overreact and say, 'I need a new coach, new physio.' I believe that if you just work on yourself and focus on yourself, you'll allow yourself to have success, no matter what else is going on around you."

Where Stephens has shown consistency is in her attitude after a loss. Relax, she told the media after her first-round loss in Melbourne in January. "It will be OK," she said. That blasé attitude has caused some people, including ESPN analyst Chris Evert, to question Stephens' desire to win more Slams. Her talent to win them has never been questioned. Remember: Stephens will arrive in New York as the defending champ. In fact, four of her five singles titles have come on hard courts, so if there's a moment primed for her to finally reveal a steady hand, the next few months could be it.

How long will it take Kevin Anderson and John Isner to recover?

Fresh off his first Slam semifinal appearance, American John Isner should ride his momentum west. Same for Anderson, who has reached the final in two of the past four Slams. But "fresh" is perhaps the wrong word to describe how either of these men will feel in the coming days.

Their six-hour, 36-minute duel Friday was the longest in Wimbledon semifinal history. For Anderson, it was preceded by a four-hour, five-set win against Roger Federer and followed by an emotional three-set loss to Novak Djokovic in the final. (Some have speculated that Isner's famed 2010 Wimbledon ultramarathon against Nicolas Mahut -- which took just over 11 hours over three days to complete and Isner won 70-68 -- took a year off the big man's career).

Whether their performances this fortnight will build momentum for the remainder of their seasons or have destroyed their bodies for the hard courts is a question even they can't yet answer. Anderson is 6-foot-8 and 32 years old; Isner is 6-10 and 33. Neither of those stats makes recovering from such punishing tennis any easier than it was for Isner eight years ago.

After Isner won the biggest title of his career at the Miami Open in April, he thanked his chiropractor, Clint, who is certain to log overtime this month. There is one light, however, at the end of the hard-court tunnel: The US Open is the only Slam that uses a fifth-set tiebreak, the tennis equivalent of penalty kicks. (Had to get a World Cup reference in here somewhere.) Fans in New York will have to wait until November if they want to see a marathon.

Is it time for the kids to step up?

It felt like Flashback Friday at Wimbledon for most of the fortnight, with the men's and women's finalists -- all of whom were over 30 for the first time in the Open era -- holding a combined 38 Grand Slam titles between them. On the men's side, the sport is especially seeing a resurgence by its power players, while the Next Gen/Under-21 set seems to be delaying its maturation.

Of the young men hailed as "next" in the sport, only Stefanos Tsitsipas, 19, and Karen Khachanov, 22, saw the fourth round at Wimbledon. Nineteen-year-old Canadian Denis Shapovalov lost in the second round, his third straight second-round exit at a Slam. World No. 4 Alexander Zverev, 21, was suffering from the flu and departed in the third round a month after experiencing his best Slam result thus far, a quarterfinal showing in Paris. American Frances Tiafoe, 20, lost in Round 3, his best performance yet at a major. So, what gives?

Katrina Adams, chairman of the board and president of the USTA, told ESPN that it takes longer for boys to develop and become strong enough to compete with the best men on tour than it does for women. "They have to get stronger before they can compete," she said. "It could happen for them at 16, or it could happen for them at 21, or it could happen even later."