Question: The 2011 Copa del Rey was a specific type of rivalry, given this name to any match between which groups?
Context: El Clásico (] ; Catalan: "El Clàssic" , ] ; "The Classic" ) is the name given in football to any match between fierce rivals Real Madrid and FC Barcelona.  Originally it referred only to those competitions held in the Spanish championship, but nowadays the term has been generalized, and tends to include every single match between the two clubs: UEFA Champions League, Copa del Rey, etc.  Other than the UEFA Champions League Final, it is considered one of the biggest club football games in the world, and is among the most viewed annual sporting events.  The match is known for its intensity. The 2015 Supercopa de España was a two-legged football match-up that was played in August 2015 between Athletic Bilbao, runners-up of the 2014–15 Copa del Rey, and Barcelona, the champions of 2014–15 La Liga and the 2014–15 Copa del Rey.  It was also a repetition of the 2015 Copa del Rey Final. The 2012 Copa del Rey de Balonmano was the 37th edition of the Copa del Rey de Balonmano.  It took place in the Palacio de los Deportes Infanta Cristina, in Torrevieja, Valencian Community, between 7 & 11 March 2012.  It was hosted by Liga ASOBAL, Torrevieja city council, Costa Blanca Tourism & Hotel La Laguna.  Torrevieja was the host team.  Torrevieja hosted Copa del Rey for second time from 2002. The 2015 Copa del Rey Final was a football match on 30 May 2015 to decide the winner of the 2014–15 Copa del Rey, the 113th edition of the Copa del Rey, Spain's primary football cup. American singer and occasional actress Lana Del Rey has appeared in three films as an actress, eighteen television shows, and three commercials, along with offering her talents to five films as singer.  Del Rey's first appearance was in the independent film "Poolside" (2010), which features Del Rey playing Lisa, a rich girl who spends her days smoking cigarettes by the pool.  She received top billing for the project.  Del Rey's next appearance was in a less-than-one-minute long short art film titled "Lana Del Rey" which was produced by Interview magazine and features noir-ish style and cinematic themes.  Del Rey's breakout appearance was in an Anthony Mandler directed film, which Del Rey wrote, titled "Tropico" (2013).  The film features Del Rey as a fictionalized version of Eve while also playing the Virgin Mary.  "Tropico" received positive reviews and was Del Rey's second film that gave her top billing.  Along with appearing in a handful of short films, Del Rey has appeared in 18 television shows and specials as herself along with appearing in campaign commercials for companies including Keds and H&M. The 1936 Copa del Presidente de la República Final decided the winner of the 1936 Copa del Presidente de la República, the 36th staging of Spain's premier football cup, now known as the Copa del Rey.  The final was the last one before the tournament was cancelled due to the Spanish Civil War until 1939, and therefore the last one under the "Copa del Predidente de la República" name. The 2011 Copa del Rey Final was the 109th final since its establishment.  The match was a traditional 'El Clásico' rivalry between Barcelona and Real Madrid which took place on 20 April 2011 at the Mestalla Stadium, making it the sixth such Copa del Rey final (the last one was played also in Valencia on 5 April 1990), just four days after the two teams played each other in La Liga and seven days before they played each other in the UEFA Champions League first leg semi-final. The 2011 Copa del Rey Juvenil is the 61st staging of the Copa del Rey Juvenil de Fútbol.  The competition began on 14 May 2011 and will end on 26 June 2011 with the final. The 1917 Copa del Rey Final was the 17th final of the Spanish cup competition, the Copa del Rey.  The final was played at Camp de la Indústria in Barcelona on May 13, 1917.  The match ended without goals after twenty minutes of extra time.  The replay match was played two days later, in the same venue with the same referee.  The match ended 1–1, and the teams decided to play twenty minutes of extra time.  Neither team scored a goal in that time, so they decided to play another twenty minutes of extra time.  Three minutes in the second extra time, Ricardo Álvarez scored for Madrid FC.  This was the fifth title for Madrid FC. The Copa del Rey de Hockey Patines is an annual Spanish rink hockey competition which is contested by eight teams.  It held every year at a neutral venue.  The first eight teams in standings just to half-season take part in Copa del Rey.  The Copa del Rey's winners play in the next edition of CERS Cup.
Answer: Real Madrid and FC Barcelona