Spanish tennis star Rafael Nadal admits that holding onto his year-end ranking as the men's world number one means a lot to him.
Nadal reached the semi-finals of the season-ending ATP Tour Finals in London by beating the inspired Swiss Stanislas Wawrinka 7-6 7-6.
But Nadal says it's even more satisfying clinching his third year-end top ranking - especially as he started the year after sitting out the second half of 2012 because of the knee injury that has dogged his career.
