The Austrian spent four days in bed with a virus after pulling out of a tournament in Doha last week.
Australian controversial tennis star Nick Kyrgios has announced that he will call curtains on his career if he wins the US Open, the fourth major of the season at Flushing Meadows.
Three-time US Open champion Djokovic, who comes into the tournament having won his fifth Wimbledon title, is followed in the seedings by 2017 winner Rafael Nadal.
Switzerland's Roger Federer, who has been hampered by back problems, has been named to play in the second singles rubber of the Davis Cup final against France's Gael Monfils on Friday, organisers announced on Thursday.
For someone who is the defending champion at Melbourne Park, Stanislas Wawrinka is remarkably upbeat about the lack of focus falling upon him.
Sumit Nagal is the only Indian in the men's field with Prajnesh Gunneswaran, ranked 132, missing out.
Murray, who suffered an elbow injury in March and made his return from a five-week layoff on Wednesday after a first-round bye, won the opening set in 48 minutes before losing concentration.
Top seed Simona Halep came back from 4-1 down in the deciding set to beat Elina Svitolina 6-3 3-6 6-4 in the Qatar Open semi-final on Friday, marking her first victory over the Ukrainian in nearly two years.
Fourteen-time Grand Slam champion Rafael Nadal crashed out of the Brisbane International after going down at the hands of top-seed Milos Raonic of Canada in their quarter-final clash here on Friday. World number three Raonic recorded only his second victory over Nadal in eight meetings with a 4-6, 6-3, 6-4 win in the last-eight contest that lasted two hours and 21 minutes.
Defending champion Angelique Kerber battled her nerves and blew a match point in the second set before finally overcoming Lesia Tsurenko 6-2, 5-7, 6-2 to reach the second round.
Andy Murray started working with former coach Daniel Vallverdu this month on a short-term basis as the multiple Grand Slam winner works towards rediscovering the form that took him to the top of the world rankings.
Greek third seed Stefanos Tsitsipas battled back from a set down to beat Serbia's Filip Krajinovic 3-6, 6-4, 6-4 in the quarter-finals of the Swiss Indoor championship on Friday. The win took Tsitsipas into his 10th semi-final of the season where he will face top seed Roger Federer, who was handed a walkover after Swiss compatriot Stan Wawrinka withdrew before their quarter-final with a back issue.
The 32-year-old world number 18 still had a remote chance of qualifying for the season-ending ATP World Tour Finals for an eighth time.
A summary of Friday's tennis action from around the world.
Jannik Sinner has sprinted past opponents at the Australian Open in his quest for a maiden Grand Slam but could end up running a marathon in the final against Daniil Medvedev on Sunday, when Melbourne Park will crown a new king.
Shapovalov pulls out of French Open.
Serbian tennis ace Novak Djokovic has continued his domination on an unchanged top 10 in the latest men's tennis rankings issued by the ATP on Monday.
World number one Novak Djokovic said his win over Rafa Nadal in Friday's epic French Open semi-final was one of the top three matches he had played and he would remember it forever.
With 1,500 points available for an undefeated champion next week, the tournament could produce a thrilling climax with Murray and Djokovic, who have never met at the O2, facing off in the final for the year-end number one ranking.
IMAGES from the matches played on Day 4 of the Wimbledon Lawn Tennis Championships at All England Lawn Tennis and Croquet Club on Thursday
Novak Djokovic and Serena Williams were named men's and women's world champions for 2015 by the International Tennis Federation on Tuesday. The Serb ended the year as men's world number one for the fourth time after taking three majors - the Australian, Wimbledon and US Open, as well as finishing runner-up to Stan Wawrinka in the French. Williams also narrowly missed a calendar-year grand slam, winning the Australian, French and Wimbledon and reaching semi-final at US Open.
Novak Djokovic and Serena Williams were named men's and women's world champions for 2015 by the International Tennis Federation.
Britain's world number two Andy Murray pulled out of the US Open on Saturday, citing a hip injury.
German seventh seed Alexander Zverev recovered from a slow start to beat former champion Stan Wawrinka 1-6, 6-3, 6-4, 6-2 in the Australian Open on Wednesday to reach his first career Grand Slam semi-final. Swiss Wawrinka, who won the first of his three Grand Slams at Melbourne Park in 2014, broke Zverev twice early in the opening set to breeze through the opening set but the 22-year-old German came roaring back into the contest.
Novak Djokovic extended his winning streak at the China Open to 27 matches with a 6-2, 6-2 demolition over big-serving American John Isner on Friday.
'During the grass court season, I unfortunately experienced a setback with my knee, and have accepted that I must withdraw from the Tokyo Olympic Games.'
Rafael Nadal has withdrawn from next week's season-opening exhibition event in Abu Dhabi due to ongoing fitness problems, the world number one said.
Third seed and Australian Open champion Wawrinka recovered from the loss of the opening set to claim his maiden Masters title on the Monte Carlo clay just six weeks before the start of the May 25-June 8 grand slam tournament in Paris.
World No 1 Novak Djokovic and Serena Williams have been named as top seeds for the US Open, which will commence from August 29.
Top seed Stanislas Wawrinka dismantled the challenge of a rampaging Aljaz Bedene with ease as the Swiss World No. 4 retained the Chennai Open title with a straight sets win in the summit clash.
Australian Nick Kyrgios was involved in a fresh dispute after being accused of swearing at the BNP Paribas Open in California.
World No 1 Novak Djokovic, on Wednesday, became the first player to earn more than US$100 million in prize money after progressing through to the quarter-finals of the French Open in Paris.
A seemingly invincible Novak Djokovic playing some of the best tennis of his career at 36 heads to Wimbledon seeking to tighten his stranglehold.
The 17-times Grand Slam champion, looking to give Switzerland their first Davis Cup title, lost his first singles rubber against Gael Monfils on Friday five days after withdrawing from the World Tour final against Novak Djokovic.
A summary of the day's tennis action at Roland Garros.
French Open champion Stan Wawrinka feels completely comfortable about his failure to break into the unofficial big four of men's tennis despite winning two grand slam titles.
American Serena Williams has also said that the dropouts will not take the shine off a potential record-equalling 24th Grand Slam title for her.
For good reason a two-week Grand Slam can be described as a 'last man standing' marathon of mental and physical endurance, which makes Roger Federer's haul of 19 all the more incredible.
Bikash Mohapatra traces the rise of the Swiss, first man to win multiple Slams in the 'Big Four' era.
In fact, barring 2014 when Stan Wawrinka won the title, no player apart from the quartet has even been involved in the men's final at Melbourne Park since 2008.
