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.
Man City drop points in chase of Arsenal, Liverpool and Man Utd also draw
Chelsea handed London rivals Arsenal a welcome boost in the Premier League title race as Enzo Fernandez struck a stoppage-time equaliser that prevented Manchester City closing the gap at the top to four points on Sunday.
Desert Vipers seal first DP World ILT20 crown after victory over MI Emirates
The Desert Vipers secured their maiden DP World ILT20 trophy after beating MI Emirates by 46 runs in front of a packed Dubai International Stadium on Sunday night.
Cameroon through to take on Morocco in Cup of Nations
Cameroon scored a goal in either half to see off South Africa 2-1 in the last 16 of the Africa Cup of Nations finals on Sunday and set up a quarter-final clash with hosts Morocco.
Bangladesh will not play T20 World Cup matches in India over 'players' safety'
Bangladesh will not play their Twenty20 World Cup matches in India after Mustafizur Rahman was released by his Indian Premier League team amid growing tensions between the countries, Bangladesh's cricket board (BCB) said on Sunday.
Root-Brook stand lifts England before weather intervenes in final Ashes Test
England enjoyed one of their better days of the Ashes series on Sunday when a 154-run stand between Joe Root and Harry Brook drove them to 211 for three before the opening day of the fifth Test was brought to a premature end at Sydney Cricket Ground.
