In several, very fundamental ways, they are the same extraordinary person.
Thirty-two years ago, Serena Williams and Roger Federer were born within seven weeks of each other. They are, at the very least, the tennis players of their generation, ruthless competitors when matches mean the most. Appropriately, they both own 17 Grand Slam singles titles.
"It's an honor to be even with Roger," Williams said after winning last year's US Open. "It feels really good to be in the same league as him. He's just been so incredibly consistent, so we have had really different careers."
Indeed, their journeys to the summit couldn't be more different. Williams learned to play on the public courts of Compton, Calif., while Federer, who was born in Basel, Switzerland, followed the more conventional path of an elite junior. Williams' slashing style is predicated on unprecedented power. Federer's game is an astonishing combination of variety and finesse.
Here's another difference: While Federer won all of his major trophies in just over nine years, Williams' swath spans 14 years and will almost certainly continue. This will be the Swiss champion's 57th consecutive Grand Slam; since winning her first, Williams has missed 10 majors -- at least one in each of eight seasons.
And there's this: Federer, ranked No. 6 among ATP World Tour players, heads into next week's Australian Open with a new coach (childhood hero Stefan Edberg) and a larger racket head (a 98-square-inch Wilson) than he's ever employed at a Grand Slam event. Last year was the first time in 11 seasons he didn't reach at least one major final. Williams, meanwhile, is the WTA's No. 1-ranked player and is favored to win this and, quite likely, every Grand Slam of 2014.
Practicing with hitting partner Sascha Bajin under the eye of her formidable father, Richard, last month in Florida, Williams asked herself what has, in recent years, become a rhetorical question:
"Why am I, like, doing this so many years later?" she related a few weeks ago at the 2014 kickoff tournament in Brisbane, Australia.
"I can't stop," said Williams. "I love being out there. I love competing. It gives me something to do. For me, it's just about motivating myself and trying to reach new goals."
Translation: Winning more Slams.
"Oh, that's going to happen," said 18-time Grand Slam singles champion Chrissie Evert from her home in Florida. "But the thing I wonder is if she can match the tennis and the enthusiasm that she had last year. It took a lot out of her. It was almost like playing three years. Every week, the focus was on her and the emotions of being excited about her place in history.
"It's not about Azarenka and Sharapova. Can Serena do it, day in and day out? It's happening to Roger Federer. It chips away, and suddenly you're not hungry. There's a point where you don't jump out of bed anymore to play a match."
Not only is Williams the oldest player ever to be ranked No. 1, but she has also been the WTA's best player for the better part of the past two years.
Since the beginning of the 2012 clay-court season, Williams has played in 27 tournaments and won 19, including four majors, an Olympic gold medal and two year-end WTA championships. Her record in that span is a fabulous 130-6. That works out to a winning percentage of .956, well ahead of the best two men over the past two seasons, Rafael Nadal (122-13, .904) and Novak Djokovic (149-21, .876).
"I see more of the same," said three-time Grand Slam singles champion Lindsay Davenport from her California home. "Serena finally understands what she can achieve. Everything is up to her. Motivation won't be a problem, but health is everything.
"Strength for strength, she's head and shoulders above everyone else."
Justin Gimelstob, who will be working his seventh Australian Open for Tennis Channel, agrees.
"I fully expect her to continue the momentum and dominance of last year," he said. "As long as she stays healthy, she's physically superior to the competition. She has the biggest weapons.
"Her belief system in the big moments -- and this X factor is impossible to quantify -- she believes in herself, and it becomes a self-fulfilling prophesy."
Williams has been dominant in the majors. Including her first Grand Slam title at the 1999 US Open, she has collected 17 singles championships -- while 16 other women have combined to win the remaining 40. Williams has won the Australian Open, Wimbledon and US Open five times each. Her work in Melbourne is unparalleled in the Open era; if she reaches the fourth round this year, she'll surpass Margaret Court's Australian Open win total of 60, the Open era standard.
It is a reasonable assumption that Williams will win at least one Grand Slam title this year, which would tie her with Evert and Martina Navratilova. If she takes two -- something she's achieved in four of the past five years -- she'll be alone in third place in the Open era, behind Court (24) and Steffi Graf (22).
That would set the table for some historic drama over the next few years.
"To be compared with Chrissie and Martina -- not yet, because I'm still not quite there," Williams said after the US Open. "I can't necessarily compare myself to them because, numbers-wise, they're still greater."
For at least a few more weeks.
With her win last week in Brisbane, Serena is working on a 22-match winning streak. She defeated the two women closest to her in the WTA rankings -- Victoria Azarenka and Maria Sharapova -- in the final and semifinal. In straight sets.
Williams enters the Australian Open as the top seed for the third time and is 14-0 in those previous events, winning the title in 2003 and 2010. This year, she clearly has the failure of last year's tournament fresh in her mind. Williams lost in the quarterfinals to then-19-year-old American Sloane Stephens.
"Always motivated to do really well in Australia," Williams said in Brisbane. "I love coming to Melbourne. Hopefully I can last a little longer."
A not-so-sweet 17
Serena Williams was already a precocious 17-year-old when she arrived at Indian Wells in March 1999. A few weeks earlier, she had beaten Amelie Mauresmo in the Open Gaz de France final, but in the pristine desert air of southern California, she was a revelation.
In the second round, Davenport was toppled in straight sets. Mary Pierce went down in the quarterfinals. Her victim in the final was Graf, who would soon win her final Grand Slam title at Roland Garros. With a steely third set, Serena won 7-5.
"For me, Indian Wells was when she solidified into what everyone thought she could be," Davenport said. "She got one of those rolls there and was playing so well. I felt more tension about playing Serena than playing Venus. Serena was a much more difficult opponent for me with her slice serve and no glaring weakness in groundstrokes, unlike Venus and her indecisive forehand."
In a week's time, three top-10 players succumbed in Indian Wells. Serena reminisced about her Indian Wells coming-out at last year's US Open.
"I have been looking at film when I was 17," she said. "Gosh, I was good. I was really -- I had no idea."
"You can feel a strong energy and determination," Graf told The Associated Press in an interview in September. "That can be definitely intimidating playing against her. You know there's a force on the court.
"Even in her young age, she and her sister, they just had a really strong presence on the court."
Even so, at the US Open most folks were focused on Venus, who is 15 months older. Including that tournament, Venus had reached at least the quarterfinals of seven of the previous eight majors. The best Serena had done was a fourth-round appearance at the 1998 French Open. The 1999 event was only her second US Open.
After coasting through her first two matches, Serena needed three sets to vanquish future Grand Slam winner Kim Clijsters. Then she defeated Conchita Martinez in the fourth round and former world No. 1 Monica Seles in the quarterfinals. Davenport fell in the semifinals, and Serena found herself in the final opposite Martina Hingis, who had beaten Venus in the 1997 final and the semifinals a day earlier.
Williams smashed Hingis off the court 6-3, 7-6 (4) with eight aces (to none) and a 36-7 advantage in winners.
Afterward, Williams said the win was "too exciting to compute."
More than 14 years later, after this year's US Open, she said, "Gosh, it was amazing winning, like, at 17. For whatever reason, I never thought that I was going to lose that year. I just knew I was going to win it."
It took a while for that feeling to return.
Sister Venus won four majors in 2000 and 2001 before Serena won her second, the French Open in 2002. It was the first of four consecutive major titles, one of the great runs in history.
That was 11 years ago. Now, she has won four of the past six Grand Slam singles titles.
A rare opportunity
A few years ago, frustrated by Williams' seemingly cavalier attitude toward the sport, Chrissie Evert wrote her an open letter.
"Just remember," she noted, "that you have in front of you an opportunity of the rarest kind -- to become the greatest ever at something."
At an age when many players are contemplating retirement, Williams found a way to get better. She got in the best shape of her life. This allowed her to hit lower-risk shots on the run, which drastically cut down her unforced errors. She has always been at her best against the highest-ranked opponents, but with only two exceptions -- losing to Stephens in Australia and Sabine Lisicki in the fourth round at Wimbledon -- Williams did not take her eye off the ball.
For the first time, it appeared she fully understood what she meant to the sport -- and what it meant to her.
"She was beyond everyone as far as athleticism and power," Evert said. "The question was all the other stuff. She went through five, six years where she was in and out of the game, distracted or injured. Tragedies in her life, going through so much adversity. It's beautiful to see her come outside the other end because she deserves it. She deserves to break my record and Martina's."
After losing to Williams in last year's US Open final (6-1 in the third set), Azarenka -- eight years her junior -- was asked if she thought Williams could catch Graf's 22 majors.
"Well, it's not something I'm really thinking about, to be honest," Azarenka said, smiling graciously. "But I think it's incredible what she's achieving. She's playing definitely her best tennis right now.
"That's just really exciting for me to be able to compete against that type of player who can be the greatest of all time."
There is a widespread feeling that Federer will finish with his present total of 17 Grand Slam singles titles. How many will Williams wind up with?
"She's got a lot of tennis left in her," Graf told The AP. "I can easily see her pass all of our records. I don't see the competition catching up to her at all.
"We'll see how mentally and physically she's able to preserve herself over the next few years. I don't think anybody's ever played that far, that kind of tennis, at her age. I'll be curious to follow her."
Like Graf's husband, Andre Agassi, Williams took a number of mental and physical sabbaticals during her career. This allowed Agassi -- who finally realized he was squandering his great gift -- to summon the fire to compete late in his career. The same thing seems to have happened to Williams.
"There is a finish line," Gimelstob points out, "but hopefully not for a very long time. A healthy, focused and motivated Serena is virtually unbeatable. At the end of the day, her consistency won't have matched Chrissie or Martina or Steffi, but her record in the biggest moments will be her legacy.
"Setting a line in Vegas, I'd put the over-under at 20 -- and take the over. I'd take four and be surprised if she isn't into the low 20s. Steffi's 22 is very plausible."
Davenport isn't sure. Awaiting the imminent birth of her fourth child, she won't be in Australia but will work Indian Wells and the French Open as a Tennis Channel analyst.
"I'd say definitely 20, and then we'll see," Davenport said. "The only concern is injuries. She wants it so badly. She won't burn out. Last year, for the first time in a long time, she played a full schedule. She fought through it. The team will have to take a look at that.
"I think she has four left in her. … That's what my head tells me now. After she wins in Australia, we can chat again."
Making it happen
It helps to have a killer instinct.
In the crucible of a Grand Slam final, only Court was better in Open era competition. The Australian was 11-1 (.917) in major finals, and Williams isn't far behind at 17-4 (.810). By comparison, Navratilova and Evert were 18-14 (.562) and 18-16 (.530), respectively.
At least in her public pronouncements, Williams has seemed, well, almost humble.
"It's always awesome and such a great honor because I don't know if I'll ever win another Grand Slam," she said after the US Open. "Obviously, I hope so. I say that every time I win one."
If we've learned one thing over the years, Serena Williams doesn't spend a lot of time hoping for things to happen. She makes them happen.
"Minimum of one, maybe two this year," Evert said. "I see her beating mine and Martina's record. I think she can match Steffi. I don't say that easily. Margaret Court? What's she need? Seven to tie? Whoa … that's asking for a lot. That's basically saying four more years.
"Not sure about that."
Two years ago, Williams was coming off a dreary 2011 season that was marked by health and injury scares and, for the first time in five years, no major titles. She slowly found her game and won the last two Slams. And then it happened again last year.
This season, will she find the fire to again extend her reign over women's tennis?
"I actually had a similar dilemma last year," Williams said a few weeks ago in Brisbane. "Does it get better than two Slams and an Olympic gold, and I think I won a couple doubles titles in there somewhere.
"I obviously looked forward to the challenge, and hopefully I can just meet that challenge again."