Andy Murray can move within sight of a semi-final place with victory over Rafael Nadal at the ATP World Tour Finals on Wednesday.
The pair will meet in their second group match at 14:00 GMT, with the contest live on BBC TV and radio.
Murray will qualify for the last four if he beats Nadal and the evening match sees any result other than a straight-set win for Stan Wawrinka.
A victory would also guarantee Murray the year-end number two ranking.
"It would be obviously nice to finish number two because I haven't done it before, but it's not a goal that I'd set for myself at the beginning of this year or throughout the whole year really," said the Briton.