Croatian Cilic, who lost last year's final to Roger Federer, underlined his credentials for another Grand Slam title bid to add to his U.S. Open triumph in 2014.
Former men's champion Mats Wilander believes third seed Muguruza now looks like the most likely champion, having not dropped a set and thrashing Maria Sharapova on Wednesday.
Djokovic is clubbed with Federer, Juan Martin Del Potro, David Goffin and Alexander Zverev.
Former world number one Novak Djokovic showed signs of a return to form with an impressive 7-5, 6-4 victory over Japan's Kei Nishikori in the opening round of the Madrid Open on Monday.
Angelique Kerber produced a stunning display of defensive tennis to see off the big-hitting Naomi Osaka 6-4 5-7 6-4 in a classic Red Group encounter between the last two Grand Slam champions at the WTA Finals on Wednesday. The victory evens up Kerber's record at 1-1 in round robin play as Osaka slumped to her second straight defeat at the season ending event, leaving the U.S. Open champion on the brink of elimination from the eight-woman tournament.
On a day when top seed Sloane Stephens survived a scare before beating Ajla Tomljanovic 4-6, 6-4, 6-4, Sakkari showcased supreme court coverage skills throughout her almost two-hour match against Bertens.
A summary of the second day's play at the US Open.
The 37-year-old has enjoyed a renaissance season that has seen her reach the Australian Open and Wimbledon finals and sit just one victory away, against American compatriot Sloane Stephens, from playing for the US Open title for the first time since 2002.
Former world number one Garbine Muguruza was beaten 7-5, 6-4 by Aryna Sabalenka in the China Open second round on Tuesday while an ailing Jelena Ostapenko lost 6-0, 6-0 to Wang Qiang.
World No 1 Novak Djokovic will face Argentina's Juan Martin del Potro, the player who denied him a medal in London, in the opening round of the Rio Olympics after the draw was made on Thursday.
Here are some of the best moments from the 2019 Australian Open.
IMAGES from the matches played during the Wimbledon Championships at the All England Lawn Tennis and Croquet Club, at Wimbledon in London on Thursday
IMAGES from matches on Day 8 at the French Open
The draw for the first Grand Slam of the season was made on Thursday and the top seeds could face some early tests of their credentials when play gets underway in Melbourne on Monday.
Newly-crowned French Open champion Simon Halep said she was inspired to win her first Grand Slam title by her manager Virginia Ruzici's feats 40 years ago at Roland Garros.
Spain's Carla Suarez Navarro came back from a dreadful first set to defeat Venus Williams.
At one stage Yuki was a break up, serving for the opening set but lost his serve and eventually the set. After drawing parity, Yuki twice lost his serve to fall behind 0-3 in the decisive set and never recovered.
A misfiring Rafael Nadal had trouble hitting the mark but the third seeded Spaniard still had enough to beat American Donald Young 6-4, 6-2 on Tuesday and advance to the fourth round of the BNP Paribas Open.
IMAGES from matches played at the Miami Masters in Key Biscayne, Florida
The fluorescent yellow outfit Victoria Azarenka wore as she dismantled Caroline Wozniacki at the Australian Open on Thursday was a one-word fashion statement -- loud.
IMAGES from the matches played at the PNB Paribas Open at Indian Wells on Sunday
A round-up of tennis matches played on Tuesday.
Sloane Stephens will be defending her title at the U.S. Open but all eyes will be on Serena Williams over the coming two weeks as the six-times champion attempts to win her first Grand Slam title since becoming a mother.
Images from Day 4 of the 2021 US Open in New York on Thursday.
World No 1 Serena Williams smashed a racquet and recovered from a set down as she overcame stubborn resistance from Caroline Wozniacki in a semi-final at the WTA Finals last week. It was not the first time the world No 1 abused her playing equipment. Take a look at previous moments when she soaked up her frustration on court by smashing her racket.
IMAGES from Australian Open matches played at Melbourne Park on Friday
The fifth-seeded Austrian, who saved two match points, will face Novak Djokovic on Saturday after the world number one's opponent Marin Cilic withdrew with food poisoning.
Ferrer, 37, announced earlier in the year he would end his 19-year career at the Madrid Open and prolonged his time on court by a day by beating Roberto Bautista Agut on Tuesday, but was easily overpowered by world number four Zverev.
The top women's seeds continued to be scattered at Wimbledon on Wednesday, with Caroline Wozniacki's exit meaning five of the top eight were gone before the end of the third day.
Serena Williams rallied to avoid a stunning upset and secure a 1-6, 6-3, 6-3 semi-final win over Czech qualifier Marie Bouzkova at the Rogers Cup on Saturday, setting up a title showdown with local teenager Bianca Andreescu.
Images from Day 3 of the French Open matches played at Roland Garros on Tuesday
Kyrgios did not face a single break point and hit 18 aces, including two to close out the final.
A fired up Naomi Broady let her racquet do the talking as she stormed back to beat Jelena Ostapenko in an ill-tempered Auckland Classic clash marred by an on-court row after the Briton called for the Latvian to be disqualified.
Roger Federer is keeping a lid on expectations.
World No 1 Serena Williams overcame a dreadful second set to beat Germany's Sabine Lisicki.
IMAGES of the all the action from Day 1 of the Australian Open played at Melbourne Park on Monday
A summary of sports events and sports persons, who made news on Monday
World number one Rafael Nadal recorded his 20th straight win on clay as he began his quest for a sixth title in Madrid, defeating Frenchman Gael Monfils 6-3, 6-1.
'Yeah, I'm a little sad. I don't know. I'm going to have my Stevie G jerseys hanging somewhere'
Sixth seed Andy Murray may feel the most aggrieved of the top contenders in the men's draw.