Serena Williams will compete at the Canadian Open among a host of star-studded names as she ramps up her preparations for the US Open.

Williams returned to Wimbledon in June in what was her first singles match since suffering injury in last year's competition at the All England Club.

The 23-time grand slam champion succumbed to a first-round elimination at SW19, though, falling to Harmony Tan on Centre Court.

While Williams, 40, could offer little assurances she would return to the British major, she suggested she would play at the US Open, stating "there's always motivation to get better and play at home".

Williams will be joined in Canada by world number one Iga Swiatek, four-time grand slam winner Naomi Osaka, French Open finalist Coco Gauff and reigning US Open champion Emma Raducanu as 41 of the top 43-ranked players descend on Toronto, with the tournament starting on August 6.

It will also mark Williams' first appearance at the event since she finished runner-up to Bianca Andreescu in 2019.

"When you read over that star-studded list, it's hard not to get excited about the WTA Tour making its return to Sobeys Stadium," said tournament director Karl Hale.

"Not only is this one of the strongest, if not the strongest, player list we've ever submitted, but it's also the first time in three years that the [Canadian] Open returns to a full capacity.

"We're thrilled that these players will have a chance to play in front of a packed house, and we're even happier for our fans who will get to watch tennis' very best at the 2022 edition."

Daniil Medvedev lived up to his top-seed billing by overcoming Reilly Opelka in straight sets in the National Bank Open final.

World number two Medvedev prevailed 6-4 6-3 in Toronto on Sunday as he became the first Russian to win the ATP tournament since Marat Safin in 2000.

Medvedev now holds four of the nine ATP Masters 1000 titles, having also previously come out on top in Cincinnati, Shanghai and Paris.

He saved all four break points faced against unseeded Opelka, who stunned Stefanos Tsitsipas in the semi-finals, and needed just 85 minutes to complete the job.

Reflecting on his latest tour triumph, Medvedev said: "I could not have dreamt of this at one point.

"With Novak [Djokovic] and Rafael [Nadal] playing, it seemed like an untouchable achievement. Now I have four wins in five finals, which is a good score. I am just happy. 

"Playing Canada and Cincinnati, the goal is to win as many matches as possible. I was able to do it two years ago and I will try and do it again."

Opelka was competing in his maiden final at this level and started strongly, racing 40-0 ahead in the fourth game with some powerful hitting.

However, the 23-year-old – the first American to reach the final since Mardy Fish in 2011 – could not break his opponent as Medvedev recovered with some impressive serving to take the game.

Medvedev earned the first break in the following game and comfortably held to take the first set.

The Russian forced Opelka into errors in the second set and reeled off nine points in a row en route to breaking his opponent in the third game.

It was plain sailing from that point on as two-time beaten grand slam finalist Medvedev eased over the line to add another trophy to his collection.

Unseeded Camila Giorgi again surprised Karolina Pliskova as she earned a straight-sets win in Sunday's National Bank Open final to claim the third singles title of her career.

The world number 71 defeated Pliskova at the Viking International and the Tokyo Olympics in the past three months and prevailed 6-3 7-5 in their latest meeting in Montreal.

Giorgi, who had never previously won a trophy above 250 level or on outdoor hard courts, has now triumphed in 16 of her last 20 matches in an impressive 2021 campaign.

She lost just one set all week and will move back into the world's top 35 for the first time since May 2019 with this first tournament victory since the Linz Open in October 2018.

Fourth seed Pliskova eliminated favourite Aryna Sabalenka in the semi-finals but could not replicate that performance as she fell at the final hurdle in a tournament for the third time this year.

Giorgi broke the former world number one for the first time in a lengthy fifth game and took the first set when Pliskova double faulted and sent a forehand wide in the final game.

Pliskova double faulted six times across the match, which lasted one hour and 40 minutes, including in the fourth game of the second set to put her opponent in complete control.

The Czech was given hope when earning her first break of serve in the following game, but she was let down by some forehand errors in the 12th game and Giorgi took her second championship point to seal an emotional win.

Top seed Daniil Medvedev will face Reilly Opelka in the National Bank Open final after the American stunned Stefanos Tsitsipas in a three-set classic in Saturday's semi-finals.

World number 32 Opelka fought back from a set down in Toronto to knock out favoured third seed Tsitsipas in two hours and 32 minutes.

The 23-year-old American triumphed 6-7 (2-7) 7-6 (7-4) 6-4, booking a spot in his first ATP Masters 1000 final.

Opelka sent down 17 aces but also hit 27 groundstroke winners in the shock victory over 2021 Australian Open semi-finalist Tsitsipas who had beaten in-form Casper Ruud in the quarters.

"I played great," Opelka said in his on-court interview. “These courts suit my game, it is no coincidence that John Isner is in the other semi-final.

"Stefanos has definitely improved his returning. Come 5-5 in the first set, a lot of balls started to come back. He is a thinker and has a high tennis IQ, so it was expected, but that is what separates him from the rest of the pack."

Opelka was aided by an excellent first serve percentage of 72 per cent, winning 62 of 81 points when he made his first serve.

Both first two sets went to tiebreaks, with Tsitsipas failing to generate a break point until the third set. Opelka made the first break of the match in the seventh game of the third set and held serve twice after to seal victory.

World number two Medvedev cruised into the decider with a commanding win over John Isner in less than an hour.

Medvedev, who was runner-up in Toronto in 2019, won 6-2 6-2 over the big-serving American, with the match totaling 54 minutes.

Isner could only manage four trademark aces for the match, while the Russian had 11 and broke the American four times from seven opportunities.

Karolina Pliskova will face unseeded Italian Camila Giorgi in the National Bank Open final after beating top seed Aryna Sabalenka in the last four.

An intriguing semi-final pitted two of the favourites against one another in Montreal and it was Pliskova, the fourth seed, who came out on top 6-3 6-4.

The Wimbledon finalist broke early in the first and then clinched the set on Sabalenka's serve, too, although she was made to work a little harder in the second.

Pliskova fell behind in the seventh game, but she responded by winning three straight games to wrap up victory.

"It's an amazing feeling to be in another final this year," Pliskova said.

"I think I was super solid today. I just did everything what I was supposed to do to win this match, played smart.

"My serve was pretty good, I have to say."

Indeed, the Czech landed 71 per cent of her first serves in – with 10 aces to two double faults – helping her to win 69 per cent of her service points.

World number 71 Giorgi progressed to the decider with a three-set win over Jessica Pegula in two hours and 11 minutes.

The 6-3 3-6 6-1 win means the Italian qualified for her first career WTA 1000 final.

Giorgi had toppled seventh seed Petra Kvitova, ninth seed Elise Mertens and 15th seed Cori Gauff on her route to the decider.

Local hope and reigning champion Bianca Andreescu blew an early lead as she was toppled by Ons Jabeur in the Round of 16 at the National Bank Open in Montreal.

Tunisian 13th seed Jabeur defeated the Canadian second seed 6-7 (5-7) 6-4 6-1 in two hours and 39 minutes on Thursday.

The come-from-behind triumph was the second time in two matches that the Tunisian has rallied from a set down to win after beating Daria Kasatkina in three.

Jabeur had twice been a break up in the opening set before Andreescu claimed it in an tiebreak.

The 26-year-old Tunisian, who made the Wimbledon quarter-finals this year, responded by breaking at 5-4 to win the second set.

After Andreescu had an injury scare after landing awkwardly on her left foot late in the second set, Jabeur dominated the third, finishing by winning eight of the final nine games.

Jabeur finished with 9-3 aces and was more effective on serve, going at an 81.6 win percentage on her first serve (40 from 49 points).

The lower side of the draw has opened up for the Tunisian who will face Jessica Pegula in the quarter-finals after the unseeded American defeated countrywoman Danielle Collins 6-4 3-6 7-5.

Two-time Wimbledon champion and seventh seed Petra Kvitova was knocked out in a shock by Italian Camila Giorgi in straight sets.

Giorgi, ranked 71st in the world, won 6-4 6-4 in one hour and 36 minutes and will face Cori Gauff in the quarter-finals after she had another walkover against Johanna Konta.

Top seed Aryna Sabalenka had no such problems, cruising past Canadian Rebecca Marino 6-1 6-3 inside an hour.

Sabalenka sets up a quarter-final clash with fellow Belarussian and two-time Australian Open winner Victoria Azarenka.

Azarenka got past Greek 11th seed Maria Sakkari in three sets, 6-4 3-6 7-6 (7-2).

Fourth seed Karolina Pliskova got past Amanda Anisimova 6-1 7-6 (10-8) and will play Sara Sorribes Tormo in the last eight after she won in three sets over Katerina Siniakova.

Casper Ruud continued his excellent winning streak while Stefanos Tsitsipas made it a birthday to remember at the National Bank Open in Toronto.

Tsitsipas turned 23 on Thursday and marked the occasion with a 6-3 6-2 win over Karen Khachanov.

The Greek star was presented with a cake by tournament officials after his win, as the crowd serenaded him with a chant of 'happy birthday'.

It marks a significant improvement on when Tsitsipas turned 20. On that occasion, he lost the 2018 final of this event to Rafael Nadal.

Next up for Tsitsipas is Casper Ruud, who poked fun at his critics after he eased into the quarter-finals.

Ruud, the world number 12, won three titles on clay courts in July and has now continued that form in the ATP Masters 1000 event.

Playing on a hard court has proved no challenge for the in-form Norwegian, who wrote 'Hard Courts' with a smile underneath on the camera after his 6-4 6-3 victory over Dusan Lajovic on Thursday.

"I have seen a lot of people questioning my ability to play on hard court, so I just thought it was funny to write a little note," Ruud said in a news conference.

"I think it's fun to play on hard courts. Even though I (have achieved) most of my best results on clay, my best slam result is from this year’s Australian Open (where he reached the Round of 16), so I think it's a surface that also can suit my game well even though this year has been mainly clay.

“I think I'm motivated to come back to the hard courts. I have had two very good matches here. It's a great start for me to the hard-court swing."

Ruud, in the hunt for his fifth title of 2021, has won the only previous meeting between the duo.

"[I am] looking forward to that battle," Tsitsipas said. "We have played each other in the past. Not an easy guy to play against. Looking for a change, looking for a switch-up this time."

However, there was no place in the last eight for world number seven - and Olympic gold medallist - Andrey Rublev, who went down 7-5 7-6 (7-5) to American John Isner.

Fresh from a triumph in Atlanta, 36-year-old Isner has looked sharp all week and has now won eight successive matches.

It brings up a third quarter-final appearance for the world number 30 in Canada, and he will play French 11th seed Gael Monfils after he got past lucky loser Francis Tiafoe 6-1 7-6 (7-2). Monfils will be competing in his first ATP Tour quarter-final in 18 months.

Top seed Daniil Medvedev proved too good for Australian qualifier James Duckworth, winning 6-2 6-4 in one hour and eight minutes.

Medvedev was in ominous form on the hard court, sending down 10-1 aces and winning 27 of 32 points on his first serve.

The Russian world number two will play seventh seed Hubert Hurkacz who fought back to win 6-7 (7-9) 6-4 6-4 over Nicolas Basilashvili.

Eighth seed Diego Schwartzman lost in three sets to 10th seed Roberto Bautista Agut after the Spaniard saved three match points.

Bautista Agut will next play Reilly Opelka who came from behind, and also saved a match point, to win over Lloyd Harris in three.

Two-time Grand Slam winner Simona Halep's return to the WTA Tour ended in defeat to American Danielle Collins in almost three hours in the National Bank Open in Montreal on Wednesday.

World number 28 Collins triumphed 2-6 6-4 6-4 over the sixth seed Romanian, with the second-round match lasting two hours and 55 minutes.

Halep, who is a two-time winner in Montreal, was returning to the Tour for the first time in three months since suffering a calf tear against Angelique Kerber in Rome.

Collins, who has won titles recently in San Jose and Palermo, loomed as a tough first-up test for Halep, who broke twice to win the first set 6-2 as she generated eight break points to one.

The game turned from then on, as Collins sent down 4-1 aces in the second set and finished with 38 winners for the match.

Tokyo 2020 bronze medalist and third seed Elina Svitolina was bundled out in a second-round shock, losing 3-6 6-3 6-2 to Briton Johanna Konta.

Svitolina boasted a 5-0 record against Konta heading into the match but was beaten in a two-hour-and-11-minute struggle.

Top seed Aryna Sabalenka defeated former U.S. Open champion Sloane Stephens in three sets to secure her third-round spot.

Sabalenka fought back from the brink, rallying to win the last five games and triumph 7-6 (7-4) 4-6 6-4 over the American wildcard in a two hours and 25 minutes.

Fourth seed Karolina Pliskova came from behind to win 4-6 6-3 7-6 (7-2) over Donna Vekic, while Jessica Pegula also fought back after a slow start to topple 10th seed Anastasia Pavlyuchenkova 1-6 6-3 6-2.

Greek 11th seed Maria Sakkari won in three sets 6-4 6-7 6-4 over Veronika Kudermetova, while 13th seed Ons Jabeur responded after a lopsided first set to win 2-6 6-3 6-4 over Daria Kasatkina.

Cori Gauff progressed after being 5-0 up as Anastasia Potapova retired, while Amanda Anisimova, Camila Giorgi, Rebecca Marino and Sara Sorribes Tormo all won too.

Canadian local hope Marino will take on top seed Sabalenka, while Gauff faces Svitolina's conqueror Konta.

Canadian fifth seed Denis Shapovalov was a major casualty in the second round of the National Bank Open in Toronto after a straight-sets defeat to Francis Tiafoe.

Unseeded American Tiafoe swept aside the local 6-1 6-4 in one hour and 15 minutes to secure his third-round spot against 11th seed Gael Monfils who beat John Millman 3-6 6-3 6-4.

Tiafoe was only in the Toronto main draw as a lucky loser after being defeated in qualifying by Emil Ruusuvuori but he hit 14 winners in an emphatic display.

World number 10 Shapovalov was unable to generate any break points while Tiafoe reeled off five games in a row, with two breaks, to win the first set.

The Canadian continued to struggle with his serve in windy conditions, as the American world number 52 won 88 per cent (23/26) of points on his first serve.

Another local hope, ninth seed Felix Auger-Aliassime, also was eliminated, going down 7-5 6-4 to Serbian Dusan Lajovic.

The Canadian hit six aces to Lajovic's none, but was undone by unforced errors at key times, with a double fault gifting the Serbian a 6-5 lead in the opening set.

Australian 12th seed Alex de Minaur also bowed out after a one-sided 6-1 6-1 defeat to Georgian world number 42 Nicolas Basilashvili.

Basilashvili sent down 6-2 aces and converted five of his six break points generated in an impressive display.

Australian qualifier Jack Duckworth booked a third-round ticket against top seed Daniil Medvedev after upsetting 16th seed Jannik Sinner, who won last week's Citi Open.

Fourth seed Andrey Rublev won through with a 7-6 (7-4) 6-3 victory over Fabio Fognini, while seventh seed Hubert Hurkacz progressed with a walkover after Kei Nishikori retired with a shoulder injury.

Eighth seed Diego Schwartzman beat Benoit Paire 7-5 6-1, while 10th seed Roberto Bautista Agut handled Tommy Paul 6-3 6-4.

John Isner knocked out 13th seed Cristian Garin in three sets, while Lloyd Harris beat Feliciano Lopez in two and Karen Khachanov defeated compatriot Aslan Karatsev 7-6 (9-7) 6-4 to secure a third-round meeting with third seed Stefanos Tsitsipas.

Tsitsipas pledged to help those affected by the fires in his homeland in his post-match press conference on Tuesday.

“My heart is with all the people of Greece,” Tsitsipas said. “I come from the south suburbs of Athens. When I was there a few days ago, I could see the fires from the south. Huge, giant clouds, smoke, which you could see from far, far away. It wasn't very nice. Even at the beach that day when I went to swim, you could see all the debris from the smoke and from the fires in the sea.”

Daniil Medvedev and Stefanos Tsitsipas survived three-set scares at the National Bank Open on Tuesday, but five-time tournament champion Rafael Nadal departed Toronto without even taking the court. 

Top seed Medvedev, who won just three games against Nadal in the final in 2019, the last time the tournament was played, prevailed 4-6 6-3 6-4 in his opener against Alexander Bublik.

The man Nadal beat to win the title the previous year, Tsitsipas, failed to convert on five match points in an epic second-set tiebreak but recovered to down Ugo Humbert 6-3 6-7 (13-15) 6-1.

Nadal pulled out ahead of a scheduled match against Lloyd Harris, who beat him last week in Washington as the 20-time grand slam winner struggled with a foot injury. 

Countryman Feliciano Lopez replaces Nadal in the draw and will face Harris on Wednesday. 

Elsewhere Tuesday, sixth seed Casper Ruud needed more than two hours to put away Marin Cilic 6-3 3-6 6-3, while 14th seed Grigor Dimitrov suffered a quick 6-3 6-4 exit against big-serving American Reilly Opelka.

A pair of unseeded veterans advanced, with 2016 finalist Kei Nishikori a 6-4 6-7 (5-7) 6-2 winner over Miomir Kecmanovic and John Isner defeating Alejandro Davidovich Fokini 6-4 6-1 in just over an hour.

Two days after appearing in his first ATP Tour final at the Citi Open, Mackenzie McDonald fell 6-3 6-4 to Benoit Paire in his Toronto opener. 

In other first-round matches, Karen Khachanov beat Cameron Norrie 6-4 5-7 6-4, Frances Tiafoe downed Yoshihito Nishioka 6-4 6-3, Dusan Lajovic handled Emil Ruusuvuori 3-6 6-3 6-3 and Nikoloz Basilashvili defeated Jenson Brooksby 2-6 6-0 6-4.

Rafael Nadal has withdrawn from the National Bank Open ahead of his opening match due to a left foot injury.

The Spaniard made a return to action on the ATP Tour last week at the Citi Open, his first outing since suffering defeat to Novak Djokovic in the semi-finals of the French Open in June.

His comeback was aimed at getting prepared for the US Open but, having lost in the last 16 in Washington to Lloyd Harris, he will not now be participating in Toronto.

"I really wanted to play here a lot, but now is the moment to make a decision, and this is unfortunately the decision that I have taken," Nadal told the media.

"I have had this issue for a couple of months, as people know.

"Of course, it is not a happy situation after all the success that I had here in Canada, not being able to play this year after missing a year. It's a tough one, but that's how it is today."

Nadal skipped Wimbledon citing the need to recover after the clay season, while the left-hander also opted out of representing his country at the Tokyo Olympics.

The five-time champion in Toronto was scheduled for a repeat meeting with Harris in the second round. Instead, his place in the draw goes to compatriot Feliciano Lopez.

South African Lloyd Harris booked a second-round date with Rafael Nadal at the National Bank Open after a straight-sets win over Canadian qualifier Brayden Schnur on Monday.

World number 49 Harris eased past Ontario-born Schnur 6-3 6-2 in one hour and 17 minutes in Toronto.

Harris sent down nine aces, winning 78 per cent of points on his first serve, converting four from four break points on return.

Nadal is a five-time champion in Toronto, winning the previous two editions in 2018 and 2019.

Marin Cilic, who won his first title for three years in Stuttgart, beat Albert Ramos-Vinolas 6-2 4-6 6-3 in two hours and 13 minutes.

The 32-year-old will face sixth seed Casper Ruud in the next round.

Fabio Fognini also needed three sets to progress, battling from behind to defeat Jan-Lennard Struff 6-7 (2-7) 6-2 6-4 to set up a meeting with Andrey Rublev.

Ugo Humbert impressed in his straight-sets defeat of Lorenzo Sonego and will next face third seed Stefanos Tsitsipas, while qualifier James Duckworth beat Taylor Fritz to secure a showdown with Citi Open winner Jannik Sinner.

Alexander Bublik defeated Briton Dan Evans in straight sets to earn a second round meeting with top seed Daniil Medvedev, while Australian John Millman will face 11th seed Gael Monfils after beating Ricardas Berankis.

Reilly Opelka came from a set down to win over Australian Nick Kyrgios, while Tommy Paul also fought back to beat Canadian Vasek Pospisil.