In announcing a 22-man party for next Wednesday's friendly against Italy at the Vicente Calderon stadium, Del Bosque said players outside that squad would have to nudge others out through high performance over the closing weeks of the season.
Asked specifically about his omission of Manchester United's £37.1million man Mata, and Spain's record goalscorer David Villa, Del Bosque made it clear that he cannot pick players who are under-performing or seeing little action.
"There have been players who have not had much continuity but we are not overly concerned right now," Del Bosque said.
"In the case of Juan, we really like him, we know his potential, but we don't have room for everyone.
"This is a list only for the match against Italy. It doesn't mean anything for Brazil 2014."
Mata is settling into life at Manchester United, after leaving Chelsea, but after being a fringe figure at Stamford Bridge he is still striving to rediscover his best form.
Torres, who scored the winning goal in the Euro 2008 final, appeared as a substitute in the 2010 World Cup final and claimed the Golden Boot at the last European Championship, was another to be left out of Friday's squad.
The Chelsea striker scored for his club against Galatasaray in midweek but his performances for Jose Mourinho's side have only been fleetingly impressive.
Del Bosque believes that in Alvaro Negredo of Manchester City, and Atletico Madrid's Diego Costa, he has a strikeforce in which he can trust.
Costa has yet to make his Spain debut, after switching nationality, having previously made two appearances in friendly internationals for his native Brazil.
He had been in Spain's squad for autumn friendlies against Equitorial Guinea and South Africa, but injury forced him to withdraw.
The new boy will be on familiar territory should Del Bosque select him, with the clash against the Azzurri to be played at his club ground. And Costa is just one behind 22-goal Cristiano Ronaldo in the Primera Division scoring charts this season, netting at just under a goal per game, which has made him impossible to ignore.
"I won't hide the fact he is a unique case," Del Bosque said. "He comes in on merit for what he has achieved for his club and we think he can help us."
The Spain boss added: "The last great test is Italy before the World Cup. The players will then have three months to do well with their clubs and get to the World Cup."
Del Bosque , who was speaking in a press conference that was broadcast on the Spanish Footballers' Association website, explained why he had recalled Chelsea full-back Cesar Azpilicueta.
While Torres is left behind in London, club-mate Azpilicueta will be looking to make a positive impression, having been absent from the Spain squad since last summer.
A natural right-back, Mourinho has fielded Azpilicueta at left-back this season, ahead of England's Ashley Cole.
"He hasn't been with us since the Confederations Cup," Del Bosque said. "His versatility suits us because he plays on both sides."
Carles Puyol was a predictable absentee, having scarcely featured for Barcelona due to fitness problems this season.
But Del Bosque would welcome a fit Puyol in Brazil.
"He hasn't been discarded," said the Spain boss. "If he plays regularly and is physically well, we have no doubts about him. He is a benchmark player."
Spain squad for friendly against Italy in Madrid on March 5:
Casillas (Real Madrid), Reina (Napoli), Valdes (Barcelona); Juanfran (Atletico Madrid), Martinez (Bayern Munich), Ramos (Real Madrid), Alba (Barcelona), Azpilicueta (Chelsea), Albiol (Napoli); Alonso (Real Madrid), Busquets (Barcelona), Xavi (Barcelona), Koke (Atletico Madrid), Thiago (Bayern Munich), Iniesta (Barcelona), Navas (Manchester City), Cazorla (Arsenal), Fabregas (Barcelona), Silva (Manchester City); Costa (Atletico Madrid), Negredo (Manchester City), Pedro (Barcelona).