Novak Djokovic survived a strong challenge from world number 73 Casper Ruud
ATP Finals, London: Serbia v Netherlands Venue: O2 Arena Dates: 8-15 November Coverage: Live text and radio commentary of all matches.
Novak Djokovic won his first match in almost two months to go through to the second round of the ATP Finals in London.
The Serb was knocked out of Wimbledon before losing his world number one ranking last month.
The 28-year-old, who said he was moving “beautifully” on Monday, fought back from a set down to beat Casper Ruud 6-7 (4-7) 6-2 6-2.
Djokovic, who won the title in London in 2016, plays Tomas Berdych on Wednesday.
Earlier on Monday, Roger Federer lost a second successive match to Angelique Kerber and Juan Martin del Potro beat Dominic Thiem.
Seventh seed Del Potro, who needs to reach the semi-finals to qualify for next month’s season-ending World Tour Finals, posted a straight-sets victory, 6-3 6-2 over 13th seed Thiem.
Federer’s inconsistent form in recent months saw him slip to 19th in the ATP Race to London standings, five places behind world number seven Del Potro.
But the Swiss, playing in London for the sixth successive year, saw a first-set comeback lead to nowhere as he was beaten 7-6 (7-4) 6-7 (5-7) 6-4 by Kerber.
World number three Rafael Nadal beat Stan Wawrinka in an all-Spanish tie-break on Monday, and is now four points clear of Federer in the ATP Race to London.
A win for Nadal over either del Potro or Wawrinka on Tuesday would see him overtake Federer in the final round-robin stage of the year-end tournament.
Djokovic was then drawn against Austrian world number 39 Ruud and had to recover from a meek start as he set up a clash with world number two Andy Murray, the two-time defending champion.
Djokovic has yet to fully recover from elbow surgery that has kept him out of the game since Wimbledon, and his return to the court was delayed after he felt discomfort during an exhibition match in Vienna two weeks ago.
Wimbledon and Olympic champion Murray, who will play Mischa Zverev in his first round-robin match on Tuesday, takes on Denmark’s former world number one Bjorn Borg, the 1986 and 1988 champion, in his opener.