Juan Mata
Mata left out of Spain squad.Reuters

Manchester United midfielder Juan Mata's hopes of earning a spot in Spain's World Cup squad suffered a significant blow after he was left out of Vicente Del Bosque's squad for the friendly against Italy.

The 25-year-old will not feature in Wednesday's match in Madrid having been overlooked in favour of Bayern Munich's Thiago Alcantara, with spots also handed to Manchester City's David Silva and Arsenal's Santi Cazorla in the 22-man squad.

Del Bosque's decision represents a huge blow for Mata, who identified his desire to feature in Brazil this summer as one of the reasons behind his decision to join United from Chelsea in January for a club record fee of £37.1m.

When asked of the role his international future played in his decision, Mata said: "It was really important.

"As you know the Spanish squad is really difficult to get in.

"Lots of players are fighting to be in the last 23 going to Brazil so I hope this is going to be a great chance for me to keep playing, to keep being fit and to keep showing to the manager of the national team that I want to be there and I have to be there."

Mata has made five appearances for United since his move but has been on the winning side on just two of those occasions as United's dismal form has continued into 2014.

While there is still time for Mata to fight his way back into contention, his omission suggests his poor season has seen his stock in Spain fall dramatically, particularly in the eyes of Del Bosque.

The Spain manager will announce a primary squad of 30 on May 13, before trimming that 25 before eventually selecting a final 23 to travel to Brazil and attempt to retain the World Cup.

In a premature move from his club, United listed Mata as one of their players to be away on international duty next week on their official website this week, a day before the official squad was to be announced.

Elsewhere in the Spain squad, there was no space for Real Madrid's Isco while Fernando Torres' struggles in front of goal at Stamford Bridge ensure he will not travel as Diego Costa prepares for his first appearance for La Roja have selected to represent them over the country of his birth, Brazil.

Chelsea Cesar Azpilicueta and Manchester City duo Alvaro Negredo and Jesus Navas join Silva and Cazorla in the squad.

Full Spain squad:

Goalkeeper: Iker Casillas (Real Madrid), Pepe Reina (Napoli), Victor Valdes (Barcelona)

Defenders: Juanfran (Atletico Madrid), Raul Albiol (Napoli), Sergio Ramos (Real Madrid), Javi Martinez (Bayern Munich), Jordi Alba (Barcelona), Cesar Azpilicueta (Chelsea)

Midfielders: Xavi (Barcelona), Sergio Busquets (Barcelona), Xabi Alonso (Real Madrid), Koke (Atletico Madrid), Andres Iniesta (Barcelona), Santi Cazorla (Arsenal), Cesc Fabregas (Barcelona), Thiago Alcantara (Bayern Munich), David Silva (Manchester City)

Forwards: Alvaro Negredo (Manchester City), Jesus Navas (Manchester City), Pedro (Barcelona), Diego Costa (Atletico Madrid)