Four-time Wimbledon champion Federer plays two-time French Open winner Nadal in an exhibition on a customized half-clay, half-grass court on this Spanish island.
"It'll be fun to find out what it's like to play on a court with mixed surfaces," Federer said Tuesday. "And it ought to be interesting to see who chooses the better tactic."
Organizers needed 19 days and $1.63 million to create the court, which divides the surfaces by halves for a unique match in which a player can receive on clay and hit a winner on grass - or vice versa.
"The result is not the most important thing. It's about having fun out there," the top-ranked Federer said.
"It's going to be exciting and a good atmosphere. It doesn't always need to be crazy serious out on the match courts."
A sellout crowd of nearly 7,000 is expected at the Palma Arena for the match, which is backed by the Balearic Islands tourism bureau.
Nadal comes from Mallorca and has the homecourt advantage.
"I like the fact that the stadium is located in Mallorca, Rafa's home," Federer said. "He has been to Basel (Switzerland) after all, and now I've got the opportunity to play at his place for once."
Federer hasn't lost on grass in four years, a 48-match run that includes four consecutive titles at Wimbledon.
The second-ranked Nadal has won a record 72 consecutive clay-court matches, including two titles in a row at Roland Garros in Paris.
Nadal holds a 7-3 career edge against Federer. He beat the Swiss star 6-4, 6-4 in the Monte Carlo final on April 22 to extend his clay court record against Federer to 4-0.
On grass, Federer leads 1-0, having beaten Nadal in four sets in the Wimbledon final last year.