Swiss tennis great Roger Federer is happy with the underdog tag as he prepares to confront Spanish arch-rival Rafael Nadal in the semi-finals at the ATP World Tour Finals in London.
Federer beated Argentine fourth seed Juan Martin del Potro 4-6 7-6 7-5 at the O2 Arena to book a second place finish in Group B and a 32nd career meeting with world No.1 Nadal.
In the other semi, defending champion Novak Djokovic, who finished Group B with a 100 per cent record after a 7-6 4-6 6-3 win over Richard Gasquet, takes on Switzerland's Stanislas Wawrinka.
Federer, a six-time Tour Finals champion, is desperate to finish one of the worst campaigns of his illustrious career with yet another triumph in the prestigious season-ending event.
But the 32-year-old knows Nadal goes into the tie as favourite after capping a remarkable 2013 return from a serious knee injury by winning the French and US Opens, as well as eight other titles, en route to securing first place in the year-end rankings.
History also favours Nadal, who leads their head-to-head 21-10 and has won 13 of their past 17 matches, including all three this year.
But Federer can take comfort from his record of winning all four of his indoor clashes with Nadal, including the 2010 final at the O2 Arena.
He says he feels being an underdog means all the pressure's on Nadal.