Japan's Naomi Osaka hits a return against Ukraine's Elina Svitolina during their women's singles match on day four of the 2016 Australian Open tennis tournament in Melbourne on January 21, 2016. AFP PHOTO / SAEED KHAN-- IMAGE RESTRICTED TO EDITORIAL USE - STRICTLY NO COMMERCIAL USE / AFP / SAEED KHAN (Photo credit should read SAEED KHAN/AFP/Getty Images)

With the last grand slam of the year about to get underway, it's time to look at the favourites, the underdogs and all the news surrounding Flushing Meadows in 2021.

Men's Singles 

Reigning champion Dominic Thiem announced earlier this week that he won't be returning to New York to defend his title after suffering a wrist injury earlier in the year. The Austrian world number 6 joins Rafael Nadal and Roger Federer on the sidelines, with the two veterans drawing the curtains on the 2021 season.

World number one Novak Djokovic seems to be the favourite going into the tournament after winning the first three slams of the year, but could potentially be underdone after a gruelling Tokyo campaign. Djokovic, who was chasing his first golden slam, lost to German Alexander Zverev in the semi-final match, eventually falling short of claiming the Bronze against Pablo Carreno Busta. The 20-time grand slam champion can still complete the first calendar grand slam since Rod Laver in 1969 should he win the US Open, though his lack of match time since the Olympics compared to his younger rivals may work against him. The 34-year-old comes up against qualifier Holger Rune in the first round, and could potentially face Zverev in the semifinals in an Olympic rematch.

Zverev, who has been considered one of the best among the next gen for most of his early career, seems to have finally emerged as the player pundits expected him to be. After taking home the gold medal in Tokyo, Zverev claimed the title in Cincinnati, dropping just one set during the tournament. The 24-year-old looks to be in career best form and full of confidence, a far cry of the sometimes inconsistent Zverev of grand slam's past. After making the final last year and losing in a close finish to friend Thiem, Zverev may be able to go one step further in 2021 and claim that elusive first slam.

Russian's Andrey Rublev and Daniil Medvedev loom as potential obstacles for Djokovic too after an impressive showing at Cincinnati, while Stefanos Tsistipas, who made the final in Paris, has had a run of good form and enters New York as a potential winner.

Reilly Opelka, playing just his third US Open, could cause trouble in the top half of the draw. The 24-year-old has had a career best season so far this year, reaching the semis in Rome and the final in Toronto, while he managed a career best third round appearance at the French Open. On home soil with a capacity crowd, should Opelka get through Kwon Soon-Woo in the first round, his section of the draw is winnable.

Women's singles

World number one Ash Barty is heading to New York after claiming her fifth title of the year in Cincinnati after a dominant final performance, sending a message to her rivals. After a disappointing singles tournament at the Olympics where Barty seemed to be under an injury cloud, the Australian looks primed to make a run at the US Open after getting considerable match time under her belt.

Naomi Osaka still looms as a threat despite missing the last two grand slams. Osaka left Tokyo earlier than she would have been hoping for and lost in the second round in Cincinnati, but the 23-year-old is a talented hard court player and knows how to win at the Arthur Ashe Stadium, the same court where she won the title in 2018 and 2020.

Serena Williams has confirmed she won't be making an appearance at her home slam. The 39-year-old is yet to rejoin the tour since withdrawing from the first round of Wimbledon with an injury, while sister Venus has also withdrawn.

Elsewhere, Aryna Sabalenka is putting together a nice 2021 campaign and looks set to make a run deep into the tournament, while Polish young gun Iga Swiatek could be a potential dark horse if she finds some hard court form.

Local hopes in the States have been given a hit despite the emergence of several young players. Jennifer Brady retired mid match against Jelena Ostapenko in Cincinnati after an injury plagued trip to Tokyo and announced her withdrawal from Flushing Meadows on Sunday local time. Fellow American Sloane Stephens, who won the tournament in 2017, looks fit coming into Monday's play after a third round run at Wimbledon, while teenage sensation Coco Gauff has had an impressive 2021 and will look to capitalise in front of a home crowd.