It's tennis on grass, but not as we know it.

This summer, Novak Djokovic and Rafael Nadal are to go head-to-head on the football pitch at Real Madrid's stadium, the Santiago Bernabeu, for a charity tennis match that could break the sport's spectator attendance record.

The July 14 showdown, a fundraiser for child and teenager poverty foundations belonging to the club and Nadal, is expected to attract 80,000 tennis aficionados, according to a statement on Real's website.

That would shatter the previous record of 35,681 fans who turned out for a 2010 exhibition match between Serena Williams and Kim Clijsters in Brussels.

"The pitch at the Santiago Bernabeu Stadium will turn into a tennis court on 14 July for a charity match between Rafa Nadal and Novak Djokovic," a club statement said.

"It will be organized by the Realmadrid Foundation and the Rafa Nadal Foundation, hoping to gather a record 80,000 crowd and collect proceeds for projects developed by both foundations."

Nadal is an avid Real Madrid supporter and is known to attend as many matches as his schedule allows.