Djokovic at his best to beat Isner in ATP finals

World No. 1 Novak Djokovic got off to a winning start on Monday in the ATP Finals in London with a straightforward 6-4, 6-3 win over American John Isner in just under an hour and 14 minutes.

Djokovic was in excellent form for the whole match and was just too good for the big-serving Isner, who didn't play badly, but had no answer to Djokovic's wide range of shots.

Perhaps the most telling statistic was that despite hitting serves of over 140 miles an hour, Isner won just 64 percent of his first serve points against Dejokvic, while he has an ATP average of winning 81 percent of the points of his first serve over the year.

A measure of the Serb's performance was the fact he won his first three service games to love in the second set, where he also put together a run of winning 19 straight points, to break the back of Isner's resistance.

The opening match of the day in the Guga Kuerton Group saw Alexander Zverev maintained his good record against Marin Cilic to beat the Croatian 7-6(5) 7-6(1) in a closely fought game.

The tournament began on Monday with two matches in the Leyton Hewitt group which saw Kai Nishikori beat Roger Federer, while Kevin Anderson defeated Dominic Thiem.

Tuesday sees the second matches from that group with Anderson facing Nishikori, while Thiem plays Federer.