Venus Williams suffered a shock elimination at the Cincinnati Masters after crashing out to qualifier Ashleigh Barty.
The 21-year-old beat Williams 6-3, 2-6, 6-2 for the first win of her career against one of the world’s top 10.
It was an error-prone performance from Williams after the 37-year-old served up six double faults, with Barty taking advantage to secure a third round encounter against Caroline Wozniacki.
The Australian said: "It's an honour to walk out on the the same court as Venus, to play against her and share the court with her.
"She's a genuine champion of the game and has, I think, paved the way for us young players coming through so to play like I did, I'm really excited."
Barty took the opening set on her fourth opportunity with a clean forehand winner, but then Williams comfortably levelled proceedings by coasting to the second set.
But the 37-year-old dropped her serve in the third and fifth games of the final set, with Barty serving out to love to seal the match.
Williams wasn’t the only high-profile casualty after former world number one Angelique Kerber succumbed 6-4, 1-6, 7-6 to Ekaterina Makarova.
Sixth seed Wozniacki reached the last 32 by beating Russia’s Elena Vesnina 6-2, 6-4, while eighth seed Svetlana Kuznetsova also progressed after a 6-3, 6-4 triumph against Yulia Putintseva.
Other winners included Madison Keys, Dominika Cibulkova, Julia Goerges, Carla Suarez Navarro, Camila Giorgi and Anastasija Sevastova.
Kei Nishikori has confirmed he will miss the rest of the tennis season due to injury.
The World No 9 withdrew from this week's Masters event in Cincinnati with a right wrist problem. Unfortunately, subsequent scans revealed a tear in one of the tendons.
While he hopes to avoid surgery, the Japanese star has been ruled out for the remainder of 2017, joining fellow top-10 players Novak Djokovic and Stan Wawrinka on the sidelines.
It's been a tough season for Nishikori, who has struggled with injuries, causing him to slip five places down the rankings.
A statement from Nishikori's manager read: "Two days ago during practice in Cincinnati, Kei hit a serve and heard a 'pop' in his wrist.
"We went straight to the hospital to take an MRI. Yesterday, we went to see a very renowned wrist specialist who works with many of the MLB baseball pitchers.
"We saw another specialist today to get a second opinion. On top of that we have sent MRI results to three other wrist specialists to ensure we get several independent opinions from specialists.
"After consulting with all of them, it has become clear that Kei has a tear in one of the tendons in the right wrist.
"At this stage we have elected not to do surgery and Kei is in a cast. After the swelling comes down in the next weeks, we will evaluate next steps. Kei will withdraw from all the 2017 tournaments and work hard to be ready for next year."
Wimbledon Champion Garbine Muguruza made short work of qualifier Beatriz Haddad Maia at the Cincinnati Masters on Tuesday, winning 6-2, 6-0, to advance to the Round of 16.
The 23-year-old fourth seed reeled off 10 consecutive games against the Brazilian to wrap up an easy win.
Muguruza now awaits the winner of the second round match between 16th seed Madison Keys and Russia’s Daria Kasatkina.
Earlier in the day, second-seed Simona Halep and seventh-seed Johanna Konta became the first players to reach the third round.
Halep defeated American qualifier Taylor Townsend 6-4, 6-1, while Wimbledon semi-finalist Konta beat Kiki Bertens of the Netherlands 6-3, 6-3.
Venus Williams breezed into the second round with a simple win over compatriot Alison Riske 6-2, 6-0 in just 66 minutes. Williams will play Australia’s Ash Barty, who beat fellow qualifier Varvara Lepchenko 6-4, 6-4.
"I hadn't played in a while, so I wasn't really sure what to expect," said Williams, who lost in the round of 16 at last week’s Rogers Cup.
"I know she likes a flat ball and is a retriever and is just feisty, and the courts are really slow, too. Today was like about being measured and being patient and trying to just capitalise on the match."
Another qualifier, Aleksandra Krunic, pulled off a surprise 6-4, 6-2 win over 12th-seed and Roland Garros champion Jelena Ostapenko, while Poland’s Agnieszka Radwanska (10) was knocked out by unseeded German Julia Goerges 6-4, 6-4.
The US Open has become the first grand slam to hand Maria Sharapova a wildcard entry to the tournament.
The Russian superstar's world ranking fell drastically during her 15 month doping ban, making her ineligible for the tennis major's based on rankings.
A number of smaller tournaments have extended invitations to Sharapova and she enjoyed a semi-final appearance at WTA Stuttgart in April, which remains her best result since returning.
The US Tennis Association released a statement on Tuesday revealing the wildcards for the US Open, which begins on 28 August.
"Her suspension under the terms of the tennis anti-doping program was completed and therefore was not one of the factors weighed in our wildcard selection process," read the statement.
"Consistent with past practice, a wildcard was provided to a past US champion who needed the wildcard for entry into the main draw. Previous US Open champions who have received US Open main draw wildcards include Martina Hingis, Lleyton Hewitt, Kim Clijsters and Juan Martin del Potro."
Both the French Open and Wimbledon declined to hand Sharapova a wildcard entry, likely due to the criticism she received for getting entries into lesser tournaments earlier this year.
The five-time grand slam winner recently withdrew from events in Toronto and Cincinnati due a forearm injury.
Sharapova's last major was the 2016 Australian Open, where she was knocked out in the quarter-finals. The 30-year-old won the 2006 US Open, beating Justine Henin-Hardenne in straight sets.
Nick Kyrgios and Juan Martin del Potro knocked out top seeds in their opening round matches at the Cincinnati Masters on Tuesday.
Australian star Kyrgios impressed in his straight set win over ninth seed David Goffin, winning 6-2, 6-3 in just 66 minutes on the hard courts of Ohio.
Kyrgios put on a powerful display on serve, notching up ten aces in the dominant win. He saved three break points in his opening service game before going on to win the final four games of the set.
The tennis bad boy then needed just one break of serve to march into the second round.
Meanwhile, del Potro came from a set down to defeat tenth seed Tomas Berdych 3-6, 7-6(1), 6-0 in two hours.
The former world number four fired 17 aces and won an impressive 88% of his first service points despite losing the opening set.
Berdych was three points away from winning the match at 6-5 and 15-all in the second set, but the Argentine turned on the class and dominated from the tiebreak onwards.
American Sam Querrey cruised into the second round of the Cincinnati Masters on Monday, defeating fellow countryman Stefan Kozlov 6-3, 6-0.
Wimbledon semi-finalist Querrey was strong on serve, dropping just four points on first serve while facing no break points
He will face the winner of the tie between Montreal semi-finalist Robin Haase and Italy’s Adrian Mannarino.
Another Italian in action was Fabio Fognini, who will play third seed Dominic Thiem in the second round after beating young Russian Daniil Medvedev 7-6(5), 6-4.
Several other Americans made it through with Querrey including John Isner (14), who got the upperhand on Serbia’s Viktor Troicki 7-6(3), 6-4, while wildcards Frances Tiafoe and Tommy Paul plus qualifier Mitchell Krueger also advanced.
Tiafoe will face form player and Rogers Cup winner Alexander Zverev in the second round after he defeated German qualifier Maximilian Marterer 6-3, 7-6(2).
Paul beat fellow American Donald Young, while Krueger breezed past Frenchman Benoit Paire 6-2, 6-1.
South Korea’s Hyeon Chung crashed out, losing 7-6(5), 6-1 to Spanish veteran Feliciano Lopez.
Rafael Nadal will return to the world number one spot for the first time in three years from Monday after Roger Federer withdrew from the Cincinnati Masters.
Federer was the only player who could have stopped the Spaniard rising to the top in place of Andy Murray.
The Swiss star pulled out after injuring his back in Sunday's Rogers Cup final, where he lost to Alexander Zverev.
Murray pulled out of Cincinnati last week with a hip problem.
Roland Garros champion Nadal will return to the top of the rankings for the first time since July 2014.
The 31-year-old crashed out of last week's Rogers Cup in the Round of 16 when he lost to Canadian wildcard and eventual semifinalist Denis Shapovalov.
Federer, meanwhile, made it the final in Montreal where he lost to the 20-year-old German.
It was the 19-time Grand Slam champion’s first tournament since winning Wimbledon for the eighth time in July.
On his missing the Cincinnati Open, Federer said: "I am very sorry to pull out."
"Cincinnati has some of the best fans in the world and I am sorry I will miss them.
"Unfortunately, I tweaked my back in Montreal and I need to rest this week."
The Cincinnati Master is the last big tournament before the US Open starts on August 28, but has been hit this year by the withdrawal of several of the world’s top players..
Murray, Kei Nishikori, Marin Cilic and now Federer have already withdrawn, while Stan Wawrinka and Novak Djokovic are out for the rest of the season.
Alexander Zverev upset Roger Federer on Sunday to win his fifth title of the year at the Rogers Cup in Montreal.
Eighth seed Zverev triumphed 6-3, 6-4 to claim his second Masters 1000 title of the season and extend his winning streak to 10 matches.
The 20-year old German smashed down six aces among his 20 winners as he took just 68 minutes to hand Federer just his third defeat in 38 matches this year and join the Swiss on five titles for the year.
Zverev has also won titles in Rome, Marseille, Munich and most recently in Washington last week.
He was in dominant form, refusing to let Federer dominate from the baseline and winning 75 percent of points on his own serve.
The talented youngster needed just two breaks of serve to claim the match, the first coming at 2-1 in the first set and the second at 3-1 in the second.
Federer paid tribute to his opponent after his defeat.
“Of course, I'm disappointed with today. I thought I would do better,” he said on-court.
“I wanted to fight a bit more and make the match a bit more tighter. I had opportunities. But Zverev played extremely well. He played well all week.”
Elina Svitolina capped a remarkable week in Toronto by beating Caroline Wozniacki 6-4, 6-0 in the final of the Rogers Cup.
The Ukrainian, who was only ranked fifth at the tournament, claimed the scalps of Wimbledon champion Garbine Muguruza and defending champion Simona Halep en route to Sunday’s final.
Those performances ensured she was brimming confidence and it showed as she broke her Danish opponent six times throughout the match.
Wozniacki served well but Svitolina’s anticipation and accurate returning ensured she was always in control of proceedings.
The title triumph is Svitolina’s fifth in her career.
On the contrary, Wozniacki has now not won since last October despite featuring in six finals in 2017 alone.
Five-time Grand Slam champion Maria Sharapova has withdrawn from next week's Cincinnati Open with a forearm injury.
The world number 149 pulled out of the Stanford Bank of the West Classic earlier this month with the injury to her forearm and will now miss Cincinnati as a "precaution" ahead of the US Open that starts at the end of August.
Jelena Ostapenko was set to be her first round opponent in one of the best clashes but she confirmed that she will miss her sixth tournament since her comeback.
"I arrived in Cincinnati yesterday eager to play. However, following the doctor’s advice on-site, as a precaution for the US Open, I am unfortunately withdrawing from the tournament with the left forearm injury I sustained in Stanford," Sharapova said.
"I want to thank the tournament for the wild card opportunity and really look forward to competing here next year."