|2019 Nitto ATP Finals|
|Venue: O2 Arena, London Dates: 10-17 November|
|Coverage: Watch live coverage of one match per day on BBC TV, BBC iPlayer and online; Listen on BBC Radio 5 Live Sports Extra; Live text on selected matches on the BBC Sport website and app. Click here for Live Guide.|
Novak Djokovic made a winning start at the ATP Finals as he chases a record-equalling sixth title and overhaul Rafael Nadal as world number one.
The Serb was imperious, beating Italian eight seed Matteo Berrettini 6-2 6-1.
World number two Djokovic can overtake Nadal to become year-end number one this week in London but must reach the final to stand a chance.
Roger Federer plays Dominic Thiem in the same group later on Sunday as the season-ending championships.
The event at the O2 Arena features the top eight players of the year who are split into two groups.
The group stage features a round-robin format with the top two players progressing to the semi-finals with the final held next Sunday.
Nadal is in Group Andre Agassi but is an injury doubt for the tournament with a stomach muscle issue, although the Spaniard said on Friday he is confident of playing.
More to follow