Serena en Venus behaalden later samen goud tijdens de Olympische Zomerspelen van Sydney door in de finale van het Nederlandse duo Miriam Oremans en Kristie Boogert te winnen. Op het US Open kwam Williams niet verder dan de kwartfinale: haar landgenote Lindsay Davenport versloeg haar met 6-4 en 6-2. Williams faces Simona Halep on Tuesday (3 a.m. ET, ESPN2/ESPN App) in the 2021 Australian Open quarterfinals, and while she's 9-2 all time against Halep and 6-0 on hard courts, she's only 1-1. Venus Williams: 2018: US Open WTA: 1/16: Serena Williams: 6-1 6-2 2018: BNP Paribas Open: 1/16: Venus Williams: 6-3 6-4.

When the Tampa Bay Buccaneers and Tom Brady walloped the Kansas City Chiefs to earn Brady his seventh Super Bowl ring, it prompted a series of 'Is Brady the GOAT of all GOATs?' conversations. Most of those greatest-of-all-time discussions ended, or should have, upon remembrance that Serena Williams exists.

Like Brady, Williams has the rings and the longevity. Her 23 Grand Slam titles are more than anyone else's in the sport's Open era -- she even won the 2017 Australian Open while pregnant -- and she has won at least one Slam in 14 different years.

But she has dominated at a consistent level that Brady and other GOAT of GOATs candidates struggle to match. While Brady was named the NFL's most valuable player and named first-team All-Pro three times each, Williams has reached No. 1 in the WTA rankings in parts of 10 different years. At one point, she spent 186 consecutive weeks at No. 1.

To the extent that age has taken effect, both the 43-year-old Brady and the 39-year-old Williams have been forced to adapt their respective games. Williams faces Simona Halep on Tuesday (3 a.m. ET, ESPN2/ESPN App) in the 2021 Australian Open quarterfinals, and while she's 9-2 all time against Halep and 6-0 on hard courts, she's only 1-1 since her 2018 return to the tour. It's worth discussing just how her game has changed and what new strengths and weaknesses have formed.

First, let's walk back through Williams' career trajectory.

Williams' career has been defined by steady quality combined with bursts of dominance. Most of her Grand Slam titles have come in such bursts -- five titles in six Slams in 2002-03, five in eight from 2008 to '10, four in six in 2012-13, then four in a row from 2014-15 -- but between explosions and occasional injuries, she has still been a force, putting together a 0.794 win percentage in Slams she didn't win, equivalent to a quarterfinal appearance like the one she has put together so far in Melbourne.

Since her return at the 2018 French Open, her Slam win percentage is 0.849. She has reached four finals and made the semifinals at last fall's US Open. She remains a steady contender. If she does win her 24th Slam, it will be with a slightly different game.

To look at how Williams' game has changed, we'll once again lean on the data created by Tennis Abstract's Match Charting Project, as we recently did in looking at Novak Djokovic's standout traits. Jeff Sackmann and a host of volunteers have charted more than 8,500 matches and 5 million points, creating layers of extra data about serves, returns, shot placement and tendencies and allowing us to get a much better idea about what makes certain players unique.

In this case, charting data can allow us to look at the same player over different periods of time.

The Charting Project has captured 209 Williams matches through the years, from her second-round loss to sister Venus Williams at the 1998 Australian Open to last week's win over Laura Siegemund in the first round. While there is a larger sample of matches from the past decade or so, by separating Williams' charted matches into three buckets -- 1999 to 2011, 2012-17 (her most concentrated run of dominance) and 2018-present -- we can take note of what has changed through the years.

Let's start with the serve

Williams' serve has always been one of her biggest strengths, and during her 2012-17 run, in which she won 10 Slams, three WTA Finals and 12 1,000-level events, it was otherworldly.

These days, it's merely awesome. She appears to have taken a little bit of sting out of it in the name of better accuracy.

Over the 52 weeks before the Australian Open, across all matches (not only those charted), Williams' serve remained a force, ranking first among the WTA's top-60 players with a 12% ace percentage (Naomi Osaka was second at 9%) and second behind Osaka in first-serve win percentage (74%). She ranked a mortal 18th in second-serve win percentage (49%), however.

As seen above, Williams' second serve has never been a particular strength. Even in the most dominant point of her career, her second-serve win percentage was slightly under 50% in charted matches. And these stats have played out in similar fashion through four matches in Melbourne: She has recorded aces 11% of the time, and her first-serve win percentage is a stellar 80%, but she has won only 43% of her second-serve points, 37% in her last two matches.

Her first serve was particularly wayward when she dropped a 6-2 set to Aryna Sabalenka in the fourth round -- she landed just 12 of 33 first serves (36%) and won just five of 21 second-serve points (24%). If her first serve isn't accurate, things could become dicey against Halep, who headed into the Australian Open ranked fourth in win percentage on second-serve return points (61%).

It might do Williams some good to break tendencies against Halep, who broke her four times in their last meeting, a straight-sets romp in the 2019 Wimbledon final. You typically know where Williams is going to serve:

• On first serves to the deuce court, she has gone wide 57% of the time since 2018. (Average across all women's charting data from 1999 to present: 42%).

• On first serves to the ad court, she has gone up the T 56% of the time (40%).

• On second serves to the deuce court, she has gone to the body 63% of the time (46%).

• On second serves to the ad court, she goes wide 50% of the time (37%).

These tendencies have shifted a bit in recent times, particularly on the second serve -- she used to vary her deuce court serves a lot more while going wide on ad courts more frequently -- but she has always held clear tendencies. It works out most of the time, but Halep is an elite returner against both first and second serve. She broke Williams three times in their 2019 Australian Open encounter, too.

Of course, Williams broke five times in that match and won in three sets.

Her returns are getting deeper

Williams doesn't dominate quite as many points as she used to, but she has figured out new ways to establish potential control anyway. This is most evident in return data.

Sackmann's charts log return depth as either shallow (inside the service line), deep (beyond the service line) or very deep (closer to the baseline than the service line). Since 1999, 29.5% of all returns in play have been logged as 'very deep,' and while Williams used to focus more on power than depth (only 22% of her returns were 'very deep' in the 1999-2011 sample), that percentage has risen to 32% since 2018. She lands her forehand in this range 34% of the time, and against Siegemund she was very deep on 39% of her returns.

Granted, hitting outright winners trumps everything. She won 42% of first-serve return points in the 2012-17 charting sample, and that average has been only 35% since 2018. In all matches in the 52 weeks before the Australian Open, she won only 43% of all return points (31st among top-60 players), 34% against first serves (52nd).

Her return has been a revelation in Melbourne, however: she has won 50% of return points, 46% against first serves. She has broken 19 times in four matches, winning 54% of break points.

It's hard to generate offense against depth, and while Williams doesn't hit as many winners these days, she does force more errors:

• On points with 4-6 shots, she's winning 16% of points via forced error (up from 12% in 2012-17), 18% on returns. In all, she's winning more rallies in this range than ever before: 51%, slightly ahead of her 2012-17 form.

• On points with 7-9 shots, she's winning 13% of points via forced error (up from 11%). She's winning far more of these rallies than ever -- 57%, up from 53% from 2012-17 and 50% from 1999-2011.

• On points with 10+ shots, she's winning 13% of points via forced error (up from 12%), though her overall win percentage in these points (43%) is the lowest of these ranges.

Infosys, which provides data for the Australian Open, logs rallies slightly differently, but she's winning 59% of rallies lasting between 0-4 shots and 51% of those thereafter. Her ability to defend and hit with depth allowed her to buy time against Sabalenka while her serve was struggling, and it could serve her well moving forward, too, not only at the Australian Open but throughout 2021.

Williams has overachieved projections thus far at the Australian Open; Tennis Abstract's ELO rankings marked Sabalenka as a solid favorite in their fourth-round matchup, just as they favor Halep (67% win probability) in the quarters. Caesars by William Hill, on the other hand, sets Williams' betting odds at -140, equivalent to a 58% chance of victory.

Odds haven't always applied to Williams' career, though. She has won 10 Slams since her 30th birthday -- Steffi Graf, Chris Evert and Martina Navratilova combined for five such titles in their 30s -- and she's still playing at a top-10 level just seven months from her 40s. And if she continues to return and defend as she has in Australia, she will remain a contender for Slam No. 24 throughout 2021.

NEW YORK -- Get ready for the latest Grand Slam installment of Williams vs. Williams. One big difference this time: The superstar siblings will be meeting in the third round at the US Open, their earliest showdown at a major tournament in 20 years.

Serena Williams set up the highly anticipated matchup at Flushing Meadows by hitting 13 aces and overwhelming 101st-ranked Carina Witthoeft of Germany 6-2, 6-2 in a little more than an hour in Arthur Ashe Stadium on Wednesday night. Hours earlier, across the way at Louis Armstrong Stadium, Venus Williams did her part with another straight-set victory, eliminating 40th-ranked Camila Giorgi of Italy 6-4, 7-5.

'Unfortunately and fortunately, we have to play each other,' Serena said. 'We make each other better. We bring out the best when we play each other. It's what we do. I think we're used to it now.'

When they play Friday, it will be their 30th tour-level encounter -- plus, of course, all those times when they traded shots from across the net as kids in California, then on practice courts all around the world. It's also soonest the sisters have played each other at any Grand Slam since their very first tour match, all the way back at the 1998 Australian Open. Venus won that one. But since then, it has been the younger Serena who has grown dominant.

The reason this match comes so early is that their rankings are not what they've been in the past. Serena is No. 26, playing in only the seventh tournament since she was off the tour for more than a year while having a baby. Even though the U.S. Tennis Association bumped her seeding up to reflect her past success, it still placed her at No. 17. Venus, meanwhile is No. 16.

'It's so young in the tournament,' Serena said. 'We would have rather met later.'

Serena leads the series 17-12, including 10-5 at majors.

Serena Williams Vs Venus Williams Us Open 2018

Both have been ranked No. 1. They have won a combined 30 Grand Slam singles trophies, 23 by Serena. They own eight US Open singles championships, six by Serena.

They've played each other in the finals of all four Slams, including at the US Open in 2001 (when Venus won) and 2002 (when Serena did).

'It's incredible what they've done. I mean, amazing, really. Obviously, there's been other siblings that have had fantastic careers in tennis, but none anywhere close to what they've managed to achieve,' said three-time major champion Andy Murray, whose first major since hip surgery ended with a four-set loss to No. 31 Fernando Verdasco. 'I'd be surprised if anything like that ever happens again.'

Serena looked much more impressive Wednesday than her sister did, but the levels of competition were also different.

Of the 82 points that went Venus' way, only 13 came via her own winners. Giorgi had 29 winners, but also 41 unforced errors and 28 forced errors.

Serena, meanwhile, put together a 30-10 edge in winners, then declared her serve much better than it has been of late.

Soon enough, her thoughts were on her next match and a certain, rather familiar foe.

'I never root against her, no matter what. So I think that's the toughest part for me: When you always want someone to win, to have to beat them,' Serena said. 'I know the same thing is for her.'

Us Open Serena Williams Schedule

In other women's matches Wednesday, defending champion Sloane Stephens rallied past Anhelina Kalinina to win 4-6, 7-5, 6-2.

Stephens set up a third-round matchup with Victoria Azarenka, the former No. 1 player who has twice been a US Open finalist.

Stephens served an ace to finally put away the 2-hour, 46-minute match against Kalinina, a Ukrainian qualifier who was playing her first Grand Slam tournament.

Azarenka had a much easier Wednesday than Stephens, reaching the third round in her return to the US Open by beating No. 25 seed Daria Gavrilova of Australia 6-1, 6-2.

The quick match meant Azarenka didn't stay out in the heat too long.

'Yeah, I'm very happy about that,' she said.

A former top-ranked player, Azarenka is playing in the tournament for the first time since 2015, after giving birth to a son.

With a ranking too low for direct entry, she received a wild card into the tournament. She is unseeded at Flushing Meadows for the first time since 2007.

Two-time major champion Garbine Muguruza built a big lead but gave it away and was stunned 3-6, 6-4, 6-4 by 202nd-ranked Czech qualifier Karolina Muchova in a match that ended after 1 a.m. on as Wednesday turned to Thursday.

Serena Williams Vs Venus Williams Us Open 2018 Tennis Youtube

Seeded women who advanced on another day with the temperature topping 95 degrees included No. 7 Elina Svitolina, No. 8 Karolina Pliskova, No. 15 Elise Mertens, No. 19 Anastasija Sevastova and No. 23 Barbora Strycova, all in straight sets.

During her post-victory media conference, which came long before Serena set foot on court against Witthoeft, Venus clearly had little interest in entertaining questions about the possible all-in-the-family match.

'It's early in the tournament, so both of us are going to be looking forward to continuing to play better,' Venus said. 'Obviously, it's definitely a tough draw.'

Information from The Associated Press was used in this report.