Spain face the vastly-improved South Americans in Malaga on Wednesday and while Del Bosque stressed there could still be changes to his roster before the June tournament in Ukraine and Poland, Torres will struggle to make the cut unless his form rapidly improves.
Losing his place with the world and European champions is the latest setback in a dramatic turnaround for the 27-year-old, who netted Spain's winner in the final of Euro 2008 against Germany but has seen his scoring touch almost completely desert him since joining Chelsea from Liverpool just over a year ago.
"His performances recently have been a bit irregular," Del Bosque told a news conference at the Spanish football federation's headquarters outside Madrid.
"It does not mean that he is not a special and charismatic player, who has represented his country many times," the former Real Madrid coach added.
"He is a lad we appreciate a great deal and it pains me to leave him out but I wanted to be fair to those lads who are pushing for a place."
Del Bosque, who is without Spain's injured all-time top scorer David Villa but hopes to have him back for Euro 2012, said he wanted to reward form players and recalled Valencia striker Roberto Soldado for the first time since June 2007.
He also handed Athletic Bilbao's 19-year-old forward Iker Muniain his first call-up to the senior squad and included strikers Fernando Llorente, also of Bilbao, and Alvaro Negredo of Sevilla.
Another notable absentee was Barcelona forward Pedro, a World Cup-winner with Spain in South Africa in 2010 whose season has been disrupted by injury.
Torres has endured a terrible run since he moved to London for a British record 50 million pounds and is unrecognisable from the player that was beloved for his scoring exploits at Liverpool and his boyhood club Atletico Madrid.
He scored one goal for Chelsea in 18 appearances last season and this season has been equally unproductive.
He has four goals in 29 appearances and has not found the net since October 19 when he grabbed two against Genk of Belgium in a Champions League match.
He scored his last Premier League goal five months ago in a 4-1 win over Swansea on September 24 - and was sent off minutes later.
His winning goal in the Euro 2008 final in Vienna, which made him an instant hero back home, seems like a distant memory.
He last struck for Spain in a Euro 2012 qualifier against Liechtenstein in September 2010 when he scored twice in a 4-0 win but has not found the net for his country in three appearances since then.
He has a total of 27 goals in 91 appearances.
"Torres should not take his bad run of form as a negative thing but as a stimulus," Del Bosque said. "Football is about being continually alive and the group always has to be alive to compete at the highest level.
"It is in no way a definitive decision. It's a basic list but
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