Top-seeded Elise Mertens pulled out a three-set win to reach the quarter-finals at the Silicon Valley Classic as all four matches went the distance on Thursday.

The Belgian, ranked 17th in the world, prevailed 6-2 4-6 6-4 over Kristina Mladenovic of France in two hours and 40 minutes to advance in San Jose.

She moves on to face the eighth seed, Yulia Putintseva, who rallied past Ajla Tomljanovic 3-6 7-5 6-3 as the Australian blew numerous chances to pull ahead by converting only two of 16 break-point opportunities.

In the bottom half of the draw, second seed Elena Rybakina remained on track with a 2-6 6-0 6-2 victory over American Claire Liu in a rematch of a second-round meeting at Wimbledon.

Rybakina next meets seventh seed Danielle Collins, a 3-6 6-4 6-3 winner over US countrywoman Sloane Stephens.

Stephens, the 2017 US Open champion, has slipped to number 67 in the world and was playing in her first tournament since Wimbledon as she prepares for a return to Flushing Meadows.

Danielle Collins eased past Shelby Rogers 6-4 6-3 to book her spot in the second round at the Silicon Valley Classic on Tuesday.

World number 36 Collins proved too strong for American compatriot Rogers, winning in one hour and 25 minutes.

Collins will meet another American in the second round, with Sloane Stephens up next.

Former U.S. Open winner Stephens beat Caty McNally 6-4 6-2 earlier in the day.

Yulia Putintseva, meanwhile, eased her way into the second round with a 7-5 6-3 win over Croatian Donna Vekic.

Putintseva will face Australian Ajla Tomljanovic in the second round after she fought back to overcome Amanda Anisimova 1-6 7-5 7-5.

France's Kristina Mladenovic won 6-4 6-4 over Han Na-Lae, while American Claire Liu won in three sets against Dayana Yastremska.

Mladenovic will face top seed Elise Mertens, while Liu meets second seed Elena Rybakina.

French Open champion Barbora Krejcikova marched through to the Prague Open semi-finals following a straight-sets victory over doubles partner Katerina Siniakova.

The in-form second seed has six titles to her name this season; three of which have come alongside Siniakova in doubles events.

Together, they have triumphed at Roland Garros – adding to Krejcikova’s singles success – as well as in Madrid and the Gippsland Trophy.

However, this was their first singles meeting at Tour level, which went with the form book as Krejcikova claimed her 18th win in 19 matches after comfortably prevailing 6-3 6-0.

The home favourite, who is still to drop a set in the Czech capital, will play Wang Xinyu in the semi-finals after the world number 147 beat Grace Min 6-3 6-3.

Serena Williams produced an emphatic fightback in the second set to eliminate Danielle Collins 6-4 6-4 and secure a spot in the last 16 of the French Open.

While the first set provided few difficulties for the 23-time grand slam winner, she found herself trailing 4-1 in the second as Collins threatened to force a decider.

But Williams channelled her frustrations impressively, and far better than her opponent, with the 39-year-old setting up a fourth-round clash with Elena Rybakina.

Williams might have had an early advantage as some brutal returns gave her three break points in just the second game of the match, but Collins came back to hold.

The first break eventually came in the seventh game of the contest, Williams squeezing a shot over after a drop shot, then guiding a return to the back of the court with Collins in no position to respond.

Although a second break in the first set eluded Williams, she sealed the set on her serve soon after.

The second set saw Collins' serve broken in the first game, but her response was emphatic, producing back-to-back breaks of her own.

That had Collins in control of the set at 3-1 up, with Williams' frustration evident at the end of almost every point and not helped by her five double faults, one of which gifted away a second break.

Williams began to use that anger for good as she played even more aggressively.

Initially Collins rode the punches well, playing Williams impressively as she forced the seventh seed out wide and then read her cross-court return to seal the fifth game to love and a 4-1 lead.

But Collins quickly fell apart, Williams winning five games on the trot as she came back from a precarious position to seal her progression, showing commendable mental fortitude along the way.

DATA SLAM: GO BIG OR GO HOME

It is fair to say Williams' serving was a little wild at times – she was looking to be aggressive to put Collins on the back foot as early as possible. However, it left her with as many double faults as aces, five apiece. Nevertheless, the three-time French Open champion got the job done, with a huge serve ultimately sealing the victory.

WINNERS/UNFORCED ERRORS

Williams – 22/20

Collins – 18/21

ACES/DOUBLE FAULTS

Williams – 5/5

Collins – 1/3

BREAK POINTS WON

Williams – 4/8

Collins – 2/4

Sloane Stephens ended her losing run to start the year with a hard-fought three-set win over France's Oceane Dodin in the first round of the Miami Open on Wednesday.

Former US Open champion Stephens, ranked 49th in the world, defeated Dodin 6-7 (6-8) 6-4 6-2.

Stephens progresses to the second round where the top seeds, including top three Ash Barty, Naomi Osaka and Simona Halep, will be introduced and she will face 28th seed Amanda Anisimova.

Danielle Collins, Wang Qiang, Alize Cornet and Caroline Garcia were among the other winners on Wednesday, while Svetlana Kuznetsova bowed out.

SLOANE FIGHTBACK

Stephens had endured a dismal start to 2021, enduring an 0-4 win-loss record to begin the year.

The 28-year-old American was made to do it the hard way against Dodin on Wednesday, dropping the first set in a tie-break.

Stephens improved on her return in the second set, winning 73 per cent of points off Dodin's second serve before running away with the match in the last.

"It's been a rough one for me lately, so I'm really pleased to get through that, fight my way through it and make it happen somehow," Stephens said post-match.

FORMER MAJOR WINNER GONE

Two-time grand slam winner Kuznetsova was the major first-round casualty, going down 2-6 6-2 6-1 to France's Alize Cornet.

Kuznetsova, who is now ranked 35th in the world, bows out with Cornet to face ninth seed Petra Kvitova.

Collins got past France's Kristina Mladenovic 6-3 6-3 with the 40th-ranked American setting up a second-round clash with 32nd seed Veronika Kudermetova.

Wang, ranked 38th in the world, also progressed despite dropping a set in a 6-1 3-6 6-3 win over Spanish qualifier Aliona Bolsova.

SECOND-ROUND MATCH-UPS

The round of 64 will commence on Thursday, with third seed Halep to face Garcia who got past another Romanian, Mihaela Buzarnescu 6-1 6-2.

Top seed Barty will be in action against Slovakia's Kristina Kucova, while fourth seed Sofia Kenin will take on former top-10 player Andrea Petkovic.

Second seed Osaka has an assignment against 77th-ranked Australian Ajla Tomljanovic, while 14th seed Victoria Azarenka is already into the third round with opponent Laura Siegemund withdrawing after her win on Tuesday.

Iga Swiatek and Coco Gauff reached the semi-finals of the Adelaide International with contrasting victories in Thursday's play.  

Reigning French Open champion Swiatek is through to the last four of a tournament for the first time since her success at Roland Garros, having spent just over an hour on court against Danielle Collins.  

Swiatek had taken the opening set and was already 3-0 in up in the second when Collins was forced to retire due to a lower back issue.  

The fifth seed will next take on Jil Teichmann, who failed to take any of the five match points that came her way during a dramatic second set tie-break with Anastasija Sevastova, though she eventually prevailed in the decider.  

Teichmann staved off two opportunities for her opponent when serving at 4-5 in the third as she claimed three games in a row to triumph, a 6-4 6-7 (10-8) 7-5 victory coming after two hours and 57 minutes.

In the other half of the draw, Gauff had to fight hard to seal her progress, having been down a set and 4-2 to Shelby Rogers.   

The 16-year-old, who came through qualifying, rallied to triumph 2-6 6-4 6-4 and reach the semis at a WTA 500 event for the first time.  

"I didn't realise how much a role experience plays until I started playing some players who are a lot older than me and they know what to do," Gauff said, per the WTA Tour's website.   

"Even when it comes to the little mind games and all that, they know what to do in those moments. So I'm just learning and picking up a few tricks and as I go."  

Gauff, who has won all three of her matches in the main draw via a deciding set, will go up against second seed Belinda Bencic, the Swiss having swept aside Storm Sanders in straight sets. 

Danielle Rose Collins will face world number one Ash Barty after beating Zheng Saisai at the WTA Adelaide International.

The American wrapped up a 7-6 (7-5) 6-1 victory and will now face top seed Barty, who will still be smarting from her surprise quarter-final exit at the Australian Open.

Barty is the reigning champion in Adelaide and will be seeking to put that loss to Karolina Muchova firmly behind her.

Collins' compatriot Shelby Rogers also prevailed, beating Veronika Kudermetova 6-3 7-6 (7-4) to set up a clash with third seed Johanna Konta.

Anastasija Sevastova overcame Caroline Garcia 6-2 6-4, while eighth seed Wang Qiang was a 6-4 6-3 winner over teenager Olivia Gadecki.