Roger Federer and Rafael Nadal have begun preparations for next week's pair of benefit exhibitions, with each man playing for free at the event sponsored by his rival's personal charity.
The clash between top-ranked Nadal and the number two Federer, who ended 2010 just a fortnight ago by winning the World Tour Finals over his Spanish rival, begins on Tuesday in Zurich's Hallenstadion.
Money raised from that night of tennis go to the Roger Federer Foundation, which works mainly in his mother's native in South Africa. A day later, the action shifts to Madrid's Caja Magica in honour of the Fundacion Rafael Nadal.
Nadal has been promoting the event in a Spanish radio interview.
"Both in Spain and Switzerland people have turned to the charity match," he told Onda Cera. It is a nice project (which) Roger and I look forward to, I am proud to help."
Nadal said that his mother has been working for weeks on the Madrid side of the series, adding that charity work is an important part of his off-tennis life.
"I have my mother and my team working on the Foundation, this will be an important part of my future.
"I have a special fondness for children, we focus a lot on them, they are the main thing. The more income we have, the more we can help."
Federer had a brief holiday in the Seychelles, where his presence brought out the island's tourism minister for a photo opportunity. Nadal was recently honoured by his hometown of Manacor on the Island of Mallorca, where he's lived his entire life.
"I always enjoy playing Rafa on the big stages and it is especially exciting when we can do it to help raise money for our foundations," said Federer.
"I am sure that the fans in Zurich, Madrid and those around the world who will catch it on TV or the internet will see some exciting tennis for a great cause."
Added Nadal: "Playing Roger is always something special for me. I think it is also special for the fans since we played great matches all these years. But to play for a special cause as we are in Switzerland and Spain in December makes it even more special since we are helping also other people"
Between them, the pair have finished the last five years at the top of the year-end ATP rankings.