MEXICO CITY, Feb. 20 (Xinhua) -- Defending champion Juan Martin del Potro has received a wild card to play at the Mexican Open as he continues his return from a knee injury, tournament officials said on Wednesday.

The 30-year-old Argentine, who is ranked No. 4 in the world, is currently playing at the Delray Beach Open in Florida, his first event since suffering a fractured knee cap at the Shanghai Masters last October.

"Juan Martin del Potro has received the last wild card available to join the main draw," tournament director Raul Zurutuza said in a statement.

"He has been determined to defend his title and has shown great progress at the Delray Beach Open," Zurutuza added.

The Mexican Open will be played in the Pacific resort city of Acapulco from February 25 to March 2.

Others to commit themselves to the ATP 500 hard court event are Spain's Rafael Nadal, Germany's Alexander Zverev and American John Isner.

However South African Kevin Anderson, Slovakian Martin Klizan, Frenchman Lucas Pouille and Bulgarian Grigor Dimitrov will be absent because of injuries.