Novak Djokovic has made the ideal start in his quest to win a record-equalling sixth ATP Finals title.
The world number two easily beat Italy's Matteo Berrettini in straight sets at the O2 Arena in London.
However, things weren't as rosy for Roger Federer, who was beaten by Dominic Thiem in his tournament opener.
It's the second year in a row that the seven-time Dubai Duty Free Tennis Championships winner has lost his opening match at the ATP Finals.
Morocco show their credentials in impressive quarter-final performance
Morocco might finally have found their straps at the Africa Cup of Nations, advancing to the semi-finals for the first time in 22 years after a 2-0 win over Cameroon on Friday and beginning to look like real prospects for a first title in 50 years.
Rosenior looks to emulate Man Utd's 'Class of 92' with young Chelsea squad
Liam Rosenior is hoping to follow in the footsteps of former Manchester United manager Alex Ferguson by transforming Chelsea's young and inexperienced squad into winners.
Sabalenka returns to Brisbane final with win over Muchova
Defending champion Aryna Sabalenka outclassed Karolina Muchova to seal a 6-3 6-4 win at the Brisbane International on Saturday and reach the final of the Australian Open tune-up tournament for the third straight year.
Hollywood-backed Wrexham knock Forest out of FA Cup in six-goal thriller
Second-tier Wrexham beat Nottingham Forest on penalties after a 3-3 draw to reach the fourth round of the FA Cup on Friday, eliminating a Premier League side for the first time in 26 years in another chapter of their Hollywood story.
Snow, freezing temperatures force cancellation of games in Germany, England
Two Bundesliga matches have been scrapped due to large amounts of snow and ice blanketing pitches across Germany, while a third-round FA Cup match on Saturday has also been postponed due to freezing conditions in Britain.
