Former world number one Daniil Medvedev set up an Adelaide International semi-final against either Novak Djokovic or Denis Shapovalov Friday with a command performance in the countdown to the opening Grand Slam of the year.

Iga Swiatek was left in tears after Jessica Pegula stunned the world number one on Friday to give the United States a 1-0 lead over Poland in the semi-finals of the inaugural United Cup.

Novak Djokovic said "it is what it is" Thursday as he faced the prospect of missing more tournaments in the United States over his refusal to have a coronavirus shot.

Former world number one Daniil Medvedev locked in an all-Russian Adelaide International quarter-final with Karen Khachanov Wednesday, while Aryna Sabalenka stormed back to book her place in the last eight.

Novak Djokovic swept to victory in his first singles match on Australian soil since being deported a year ago, crushing Constant Lestienne at the Adelaide International on Tuesday to kick-start his bid for another Grand Slam title.

World number two Rafael Nadal slumped to a second-straight defeat at the United Cup Monday in a setback to his Australian Open preparations, but Stefanos Tsitsipas and Iga Swiatek were both on song.

Tennis fans gave Novak Djokovic a raucous welcome during his first match in Australia in almost two years when he made a rare doubles appearance at the Adelaide International on Monday.

Daniil Medvedev on Sunday admitted he would rather be playing at the mixed teams United Cup than the Adelaide International, but the Russian intends to make the most of the season-opening event.

Rafa Nadal brushed off talk of retiring anytime soon after the 22-times Grand Slam champion was stunned by Cameron Norrie in the United Cup mixed team tournament on Saturday, saying he still enjoyed competing at the highest level.

Rafael Nadal lost his opening match of the season Saturday in the countdown to the defence of his Australian Open title, but women's world number one Iga Swiatek cruised to victory at the United Cup.

Nick Kyrgios said he withdrew from the inaugural edition of the United Cup to be in peak condition for next month's Australian Open, adding that he did not expect everyone to understand the reasoning behind his decision.

Novak Djokovic admitted Thursday that being deported from Australia was an experience he will never forget, but it was time to move on, as he enjoyed a warm welcome in Adelaide.

Roger Federer has only been retired for three months but the eight-time Wimbledon champion is having to get used to ordinary life including being turned away unrecognised at the All England Club.

Novak Djokovic said  winning a record-equalling sixth ATP Tour Finals title on Sunday was a "deeply satisfying" ending to his troubled and truncated year.

Wimbledon will relax its strict rules on white clothing at the championships and allow women players to wear dark undershorts and relieve a potential source of anxiety when they have their periods, the All England Club said on Thursday.

Rafael Nadal says he is "going to die" trying to return to the level of tennis that saw him capture a record 22 Grand Slam singles titles after his hopes of a first-ever ATP Finals title and becoming year end world number one were extinguished on Tuesday.

Holger Rune said beating Novak Djokovic in the Paris Masters final on Sunday was the icing on the cake in a week where he bagged his first Masters title and became the first Danish man to crack the top 10 of the ATP rankings.

Novak Djokovic said his Wimbledon triumph gave him a much-needed boost of confidence during a tough season and that it laid the platform for a strong finish to the year.

Serena Williams on Monday said she has not retired from tennis and that the chances of her returning are "very high" after she previously indicated that she would step away from the sport after last month's U.S. Open.

Novak Djokovic believes his prolonged but self-inflicted absences in 2022 make him even more "super-pumped and motivated" to finish a year which started with the ignominy of deportation from Australia on a high.