Simona Halep says she is no longer afraid of coronavirus after getting vaccinated and hopes more players will take the jab.

Halep opted against travelling to New York for the US Open last year due to the pandemic before testing positive for COVID-19 last October.

The two-time grand slam champion missed the French Open and Wimbledon this year with a torn calf muscle, but claimed her first win since May at the Western and Southern on Tuesday, beating Magda Linette 6-4 3-6 6-0.

Former world number one Halep revealed she feels much more comfortable back on the circuit after taking the vaccine.

"I don't feel afraid, because I am vaccinated," The Romanian told reporters. "I feel protected. I am taking care. I wear the mask when many people are around."

Players have faced strict protocols since the tour resumed, with the challenges of staying in biosecure bubbles and playing in empty stadiums last year before restrictions gradually eased.

Stefanos Tsitsipas this week said that he would only take the vaccine if it becomes mandatory to play on the ATP Tour after Novak Djokovic stated he hopes it will not become a requirement to take the jab.

Halep hopes fellow professionals take the vaccine so they do not face such strict protocols.

"I don't like the bubbles," Halep said. "I feel very stressed when I'm in the bubble.

"So if people can vaccinate more and more (it) will be better, because we will not have more restrictions anymore."

Simona Halep, a three-time runner up in Cincinnati, claimed her first win since May by overcoming Magda Linette 6-4 3-6 6-0.

The 12th seed has just returned from a calf muscle tear which saw her miss the French Open and Wimbledon, and was defeated by Danielle Collins in Montreal last week.

However, at 1-4 down in the second set she required medical attention for what she described as a "sharp pain" in her right leg, but after a rain delay, the Romanian came out of the blocks to claim a third-set bagel.

Halep progressed to the Round of 32 where she will play American Jessica Pegula.

Sunday's breakthrough National Bank Open winner Camila Giorgo was beaten in straight sets by Pegula 6-2 6-2.

Former world number one Victoria Azarenka needed only one hour and nine minutes to dispose of Ludmilla Samsonova and seal her spot in the last 32.

The Belarussian triumphed 6-2 6-3 over the Russian, dominating her first serve and breaking Samsonova five times throughout the match.

Tokyo 2020 gold medalist Belinda Bencic eased past Marketa Vondrousova 6-3 7-5 continuing her bright recent run, winning in one hour and 27 minutes.

In the final match of the day's play, Caroline Garcia defeated 2017 U.S. Open champion Sloane Stephens 7-6 (9-7) 4-6 6-4 in two hours and 33 minutes.

Dayana Yastremska, Bernarda Pera, Karolina Muchova, Ons Jabeur, Elena Rybakina, Veronika Kudermetova and Coco Gauff were all winners too.

Fifth seed Matteo Berrettini survived an early scare on his return from a thigh injury to progress in the second round of the Western and Southern Open in Cincinnati over Albert Ramos-Vinolas on Tuesday.

The Italian world number eight, making his ATP Tour return since losing the Wimbledon final to Novak Djokovic in July, won 6-7 (5-7) 6-3 7-5.

The Spaniard claimed the first set in a tie-break but Berrettini hit back, sending down 25 aces for the match, winning 84 per cent on his first serve.

"I'm happy for the win. I think I served really well," Berrettini said. "My strokes from the baseline weren't working the way I wanted them to, but I knew from the beginning it's been a long time since I played a match, especially on hard, so I expected to feel a little bit weird."

The match extended to two hours and 20 minutes, with the Italian utilizing his backhand slice in the final set to get the edge.

Berrettini, who has a 33-7 record for the season, will face 12th seed Felix Auger-Aliassime or Karen Khachanov in the third round.

"I'm really happy that I'm going to have the chance to play another match because that's what I need," Berrettini said. "I need to play matches. I need to get in the best shape possible."

Canadian sixth seed Denis Shapovalov suffered a shock early upset, going down to France's Benoit Paire 6-3 4-6 7-5 in the Round of 64.

Former US Open, Wimbledon and Australian Open semi-finalist Grigor Dimitrov toppled 13th seed Roberto Bautista Agut 6-3 6-4 in one hour and 21 minutes.

Fellow seed Cristian Garin also bowed out, losing 4-6 6-3 6-4 to qualifier Tommy Paul, while ninth seed Hubert Hurkacz defeated Alejandro Davidovich Fokina 6-1 6-7 (3-7) 6-1.

Marin Cilic, John Isner, Sebastian Korda, Gael Monfils, Reilly Opelka, Lorenzo Sonego and Frances Tiafoe were the other Tuesday winners.

Isner sent down his 13,000th career ace in his three-set win over Briton Cam Norrie.

Stefanos Tsitsipas has indicated he will only get the COVID-19 vaccine if it becomes mandatory to participate on the ATP Tour.

World number three Tsitsipas revealed he has not yet been jabbed against coronavirus with the tennis world divided on the issue. 

The ATP Tour have publicly encouraged players to get vaccinated, but Novak Djokovic is among the high-profile players to have stated it should not be compulsory to compete.

When asked ahead of the Western and Southern Open if he would get the vaccine, Tsitsipas told a media conference he still had reservations.

"No one has told me anything. No one has made it a mandatory thing to be vaccinated," the Greek said.

"At some point I may have to, I'm pretty sure about it, but so far it hasn't been mandatory to compete, so I haven't done it, no."

Tsitsipas received a bye through to the second round in Cincinnati, where he will play either Sebastian Korda or Laslo Dere.

The 23-year-old, who has a tour-high 45 wins this season, climbed up to third in the world rankings last week and boldly targeted overhauling Djokovic in top spot.

"The rankings are there for a reason. They signify something important," he added.

"I think that the very next step would be the number one spot, which I hope I can get to one day.”

Petra Kvitova was one of a handful of seeded players to take the court at the Western and Southern Open on Monday and came away victorious against a past champion of the event. 

The 11th-seeded Kvitova defeated 2019 Western and Southern winner Madison Keys 7-5 6-4 on a rain-plagued opening day of main-draw play at the tournament outside Cincinnati, Ohio. 

The Czech saved eight of nine break points against her serve while breaking Keys three times, and that was enough to pull out the victory. 

Kvitova's countrywoman Barbora Krejcikova, the ninth seed, made her singles debut at the WTA 1000 event with a 6-3 6-2 rout of Daria Kasatkina. 

Fifteenth seed Elise Mertens also was a straight-sets winner, taking down Nadia Podoroska 6-3 6-4, while 13th seed Jennifer Brady defeated Ekaterina Alexandrova 6-3 7-6 (7-3) in a match that finished shortly before 1 a.m. local time.

Though only Krejcikova was in action Monday, the field in Cincinnati includes nine of the top 10 players in the rankings, led by Ashleigh Barty and Naomi Osaka in their first appearances since the Tokyo Olympics. 

In other matches on the first day of play, Heather Watson defeated Aliaksandra Sasnovich 6-2 3-6 6-1, while Paula Badosa outlasted Petra Martic 4-6 6-4 7-6 (11-9) in a two-hour, 34-minute marathon. 

Yulia Putintseva breezed past Zhang Shuai 6-2 6-0, Jelena Ostapenko beat Tamara Zidansek 7-5 6-1 and Jil Teichmann downed Sorana Cirstea 6-2 6-0. 

Angelique Kerber beat Maria Sakkari 6-2 6-2, with Alison Riske matching that scoreline in a defeat of Leylah Fernandez.

Shelby Rogers won 6-4 2-1 when her countrywoman Danielle Collins retired with an injury. 

Andy Murray looked sharp in his first singles match since Wimbledon, rolling to a straight-sets win over Richard Gasquet at the Western and Southern Open. 

Murray defeated the veteran Frenchman 6-4 6-4 on a rainy opening day in Cincinnati, capitalising on a strong service game to advance. 

Murray had 14 aces to just two double faults and won 81 per cent of points on his first serve while saving four of the five break points he faced. 

A two-time champion at the ATP 1000 event, he will face the winner of Tuesday's match between Alejandro Davidovich Fokina and ninth seed Hubert Hurkacz in the second round. 

Two players who shared a birthday Monday also prevailed on their big day. 

On the day he turned 20, 11th seed Jannik Sinner defeated Federico Delbonis 6-2 7-5, while 10th seed Diego Schwartzman had to work a bit harder on his 28th birthday to down Daneil Evans 6-2 4-6 6-3. 

Elsewhere, 12th seed Felix Auger-Aliassime beat Marton Fucsovics 7-6 (7-0) 6-3, while 14th seed Alex de Minaur rallied to down Filip Krajinovic 0-6 6-4 6-4. 

Fifteenth seed David Goffin fell 6-3 6-3 to Guido Pella in the only seeded upset of the day. 

Other winners Monday included Karen Khachanov, Fabio Fognini, Lloyd Harris, Dominik Koepfer, Benoit Paire, Albert Ramos Vinolas and Mackenzie McDonald. 

Among those set to play their opening matches Tuesday are third seed Alexander Zverev, who will face Harris, and sixth seed Denis Shapovalov, who plays Paire. 

Naomi Osaka was reduced to tears on Monday in her first WTA Tour news conference since snubbing the media at the French Open.

Osaka withdrew from the second grand slam of the year at Roland Garros almost three months ago after declaring she would not fulfil press conference duties during the tournament.

The four-time major champion cited mental health concerns for reaching that decision and skipped Wimbledon before returning to action at the Tokyo Olympics on home soil.

Osaka, who revealed in Paris she had suffered "long bouts of depression" since winning the US Open in 2018, agreed to speak to the press as she prepares return to the WTA Tour at the Western and Southern in Cincinnati this week.

The world number two was emotional after being asked how she benefits from a high-media profile but does not like talking to media.

Osaka answered the question from the journalist, but the video call was paused as she cried before later resuming the press conference.

She said before pausing: "That's interesting: I would say the occasion, when to do the press conferences is what I feel is the most difficult.

"I'm actually very interested in that point of view. For me I feel this is something I can't really speak for everybody, I can only speak for myself.

"But ever since I was younger, I've had a lot of media interest on me, and I think it's because of my background as well as how I play.

"Because in the first place I'm a tennis player, which is why a lot of people are interested in me. So I would say in that regard I'm quite different to a lot of people, and I can't really help that there are some things I tweet or say that create a lot of news articles or things like that.

"But I would also say, I'm not really sure how to balance it too, I'm figuring it out at the same time as you are, I would say."

Osaka then broke down while the next question was being put to her, but was able to continue.

The 23-year-old was given a first-round bye in what will be her first WTA tournament since the French Open.

Novak Djokovic will not play at the Western and Southern Open after a "taxing" run that has brought him to the brink of a calendar Grand Slam.

The world number one's bid for a Golden Slam faltered at the Olympic Games as he lost to Alexander Zverev in the semi-finals in Tokyo.

Djokovic appeared to tire badly and finished fourth in both the men's singles event and the mixed doubles, opting out of the bronze medal match in the latter.

But victories at the Australian Open, French Open and Wimbledon mean 2021 is still on course to be the best year of Djokovic's career.

And the Serbian is taking a little time to prepare himself for the final push at Flushing Meadows, meaning no appearance in Cincinnati next week.

"Dear fans," he wrote on Twitter. "I wanted to share with you that I am taking a bit longer to recover and recuperate after quite a taxing journey from Australia to Tokyo.

"Sadly, that means I won’t be ready to compete in Cincinnati this year, so I'll turn my focus and attention to the US Open and spend some more time with family.

"See you in New York soon!"