Serena, Djokovic, Nadal highlight storylines to watch at Wimbledon

Will Serena Williams be able to lock down a record-tying 24th major singles title? EPA/NIC BOTHMA

While both the ATP and WTA tours still have Wimbledon tuneup events in progress this week, the major ones were played last week. They certainly were eventful, with Ashleigh Barty and Felix Auger-Aliassime, two of the newest young stars on either tour, positioning themselves as contenders for the Big Show that begins July 1. Both players loom large in the storylines for Wimbledon, but they're by no means the only ones we're wondering about. Here are half a dozen of the main storylines heading into next week:

Serena's last best chance

Last year on the eve of Wimbledon, doubts surrounded Serena Williams' health, as well as her ability to go the distance in majors. She proceeded to belt her way to the Wimbledon final, even though she took a tough loss there to Angelique Kerber. No matter, many thought. Williams was back. Surely, she would lock down that elusive, record-tying 24th Grand Slam singles title -- if not at the US Open, then soon enough. It hasn't happened yet, and now it seems that Williams might be running out of time, but she also may be draining that once seemingly unlimited supply of motivation.

Williams was beaten in the third round of the French Open in a match that was as unremarkable as it was unexpected. In a moment of sober reflection afterward, Williams said she felt "super short of matches" and "pretty far away" from her best, adding: "I have some time on my hands, so maybe I'll jump in and get a wild card at one of these grass-court events and see what happens."

Williams never did take a wild card. She will go into Wimbledon cold. Let's be clear: The 37-year-old all-time Open Era Grand Slam singles champ has earned the right to do as she pleases, including drop in to play if and when she wants, for whatever reason she wants. But unless she's withholding information, it remains a question whether she can nail down that next major.

Djokovic in command

Like his fellow elites, Novak Djokovic isn't above becoming peevish, jousting with the chair umpire and undermining his own cause when things -- not necessarily scoreboard things, but other elements -- displease him. He succumbed to that temptation at the French Open in his semifinal against Dominic Thiem, forgetting for a moment that both players were obliged to deal with the horrific weather conditions (spitting rain and gusts that, at one point, sent an umbrella flying across the court). Attitude probably played a role in his loss, that savage wind also blowing away a chance at his second non-calendar year Grand Slam.

Give Thiem plenty of credit. He has been -- arguably -- the second-best player on clay behind Rafael Nadal for some time. Yet even in his distracted state, Djokovic stayed with Thiem, shot for shot, step for step. Djokovic didn't lose a set at Roland Garros before the semis. He played marvelous tennis on what arguably is his third-best surface, saying in his post-semifinal interview, "I don't think I have done too much wrong in the entire tournament. The match was always going to be tough."

So set aside any thought of Djokovic being off his feed because of those lackluster performances in the two big North American hard-court Masters in the spring and his failure to win the French Open. The pressure of the "Nole Slam" is off, and Djokovic is back on the surface (grass) he has mastered. The only top-five player who has beaten Djokovic on grass since Roger Federer last defeated him at Wimbledon in 2012 is Andy Murray, who isn't fit for singles again yet.

All eyes on Barty

A lot of people reading that Barty is the new WTA No. 1 are likely to think, "Is she for real?" It's understandable. As recently as March, even keen tennis fans knew little about her, save for the fascinating backstory involving burnout, a bout of professional cricket and an incrementally successful comeback. Then the 23-year-old went off like a bottle rocket. She won the Miami Open, the French Open, and, with her win on Birmingham grass Sunday, she locked down the No. 1 ranking -- a tribute not only to Barty but to the parity in today's WTA.

But will Barty contend at Wimbledon? The short answer: Is Rod Laver a lefty? The long answer: Yes, but she can use a little more grass-court experience against big hitters, and she'll probably need to call on significant reserves and stamina during the fortnight.

Young Australians since the 1980s have trained mainly on hard courts. But grass, like doubles (at which Barty also excels), is in the Aussie DNA. Barty, who won the Wimbledon junior title at age 15, recently told the Sydney Morning Herald: "Once I get back on the grass, I feel like a different person. It's a different tennis match, a different way that the ball is struck and it comes through. I feel extremely comfortable on it."

But at 5-foot-5½, Barty is also the shortest woman in the top 25. Her touch, variety, mobility and tactical instincts -- all extremely useful tools on grass, where the ability to improvise is at a premium -- are superb. But she has been playing an awful lot of tennis, so long matches and/or going deep in the tournament might exact a heavy toll. The same build that allows her to scoot around the court and play those low balls effectively also leaves her vulnerable to bigger players with shutdown power (think Serena Williams or Petra Kvitova).

Bulletin board material for Nadal?

Wimbledon is the only Grand Slam tournament that departs from the rankings when it seeds, using a transparent math-based formula that gives extra weight to a grass-court performance. As a result, Federer, who won on grass at Halle for the 10th time Sunday, will be seeded No. 2 behind Djokovic -- even though Nadal (who will be seeded No. 3) will still be ranked No. 2 in the world.

Nadal will take that in stride. He has bigger fish to fry.

For most of us, the big question in the Wimbledon draw when it comes to the Big Four minus Murray is: Whose side of the draw will Nadal end up on? The question has special poignancy this year for a reason that isn't immediately obvious. If Nadal and Federer end up on opposite sides, there's a reasonable chance they might meet in the final. It could be the most significant -- and hyped -- Fedal final in a decade.

That's because with his win at the French Open, Nadal has quietly crept within two Grand Slam titles of Federer (20-18). A Wimbledon win by Nadal closes the gap in the race to GOAThood to one precious major title. A win by Federer just might put the title count out of 33-year-old Nadal's reach.

Federer's grand plan to use clay to round himself into better shape (as if he wasn't already a Ferrari among, mostly, Kias) seems to have paid off. He looked sharp in Halle, quickly solving what little trouble the transition from clay to grass presented. When he secured his record 10th title in the German city, he told reporters, "I feel young again."

Nadal isn't feeling too bad these days, either. His knees seemed to hold up fine through the French Open, and he launched his preparation for Wimbledon by training at last week's WTA Mallorca Open. "Playing on the grass of Wimbledon after playing on clay is the most radical transition there is in tennis," Nadal said. "But I am happy with the adaptation to that surface that I have made during these four days [on the tournament site]."

Of course, there's also this little matter of Djokovic, but Fedal fans can dream, can't they?

So many champions, so few favorites

Depending on how generous Wimbledon is with its wild cards, there could be as many as 15 current or former WTA Grand Slam singles champions in the draw, ranging from No. 1 Barty to No. 132 Samantha Stosur. But the chore of choosing one or more favorites is a daunting one.

The job becomes a little easier when you narrow it down to the former champions. But that's a variegated bunch that doesn't necessarily bring a great deal more clarity to the picture. That cohort consists of defending champion Kerber, Serena and Venus Williams, Kvitova, Garbine Muguruza and Maria Sharapova.

Kerber has been solid, but nothing more, clinging to her No. 5 ranking without having won a tournament this year. Serena is an enormous question mark (see above) and Venus is 39 years old, down to No. 44 in the world and just 14-7 this year. Kvitova, a two-time Wimbledon champ, had a great start this year but has been sidelined with an arm injury and might not be fit for Wimbledon. Muguruza is showing signs of life, while Sharapova is 32 and just back from a lengthy injury layoff. She's 1-2 on grass during the past year.

Given these details, does anyone think a former Wimbledon champion has an edge on, say, Simona Halep, Sloane Stephens, Naomi Osaka or Karolina Pliskova?

A New Wimbledon 'trivalry'?

Forget Djokovic, Federer and Nadal. Think: Alexander Zverev, Stefanos Tsitsipas, Auger-Aliassime. One of this Next Gen trio could very well make a major impact or even win Wimbledon. The three of them could well rule the courts in the future. It's an interesting and relatively new development. Remember when the heavily hyped Next Gen fleet of players were mere specks in 22-year-old Zverev's rearview mirror? Tsitsipas and Auger-Aliassime -- the ones who are pushing Zverev, hard -- aren't even the ones whose names were on our lips.

While still entrenched at No. 5, Zverev has been struggling. In his two grass events on home soil in Germany, he lost in his first match at Stuttgart and failed in the third round at Halle (he had been to two finals there in previous years). Worse yet, he's having problems with, of all things, a younger player -- 20-year-old Tsitsipas.

The "Greek Freak" has been breathing down Zverev's neck. Tsitsipas is 2-1 against Zverev. He has risen to No. 6 in the rankings. And he's showing signs of doing what Zverev is accused of falling short at -- coming up big in majors.

Tsitsipas, though, has problems of his own with a younger dude. Auger-Aliassime, just 18, is 2-0 against Tsitsipas. The most recent of those wins was on grass just days ago in London at Queen's Club, where Auger-Aliassime went on to play (and lose) in the semifinals. The Canadian youngster has major grass-court game.

It will be fascinating to see which of the three survives the longest at Wimbledon.