World number one Rafael Nadal has been forced to withdraw from the ATP Finals due to a knee injury.
A stricken Nadal lost his opening match at the O2 Arena in London, the 16-time grand slam champion upstaged by David Goffin in three sets on Monday.
Nadal – who was already in doubt for the season-ending event after a knee injury meant he had to pull out of the Paris Masters – looked uncomfortable in the 7-6 (7-5) 6-7 (4-7) 6-4 defeat in Group Pete Sampras.
"My season is finished," said the Spaniard. "I had the commitment with the event, with the city, with myself.
"I tried hard. I did the thing that I had to do to try to be ready to play. But I am really not ready to play.
"I tried, but [it] seriously was a miracle to be very close in the score during the match."
Fellow Spaniard Pablo Carreno Busta has replaced the 31-year-old reigning French and US Open champion as an alternate.
Nadal's exit has opened the door for 19-time major winner Roger Federer to claim a record seventh ATP Finals crown.