The former Atletico Madrid and Liverpool frontman has been in disappointing form at Stamford Bridge and it has now cost him a place in the national team set-up
The 27-year-old has been unable to hit top form since joining Chelsea from Liverpol in January 2011 in a reported €58.5 million deal.
He scored two goals during Spain's Euro 2012 qualifying campaign, and Del Bosque explained that the former Atletico man needs to improve his game.
"This is a break for him, no doubt, but it should serve as encouragement," Del Bosque told reporters at a press conference. "Players should not get relaxed. This is not a final list for Euro 2012."
This is the first time in five years that Torres has been left out of a Spain squad for reasons other than injury.
Real Madrid defender Raul Albiol and Barcelona attacker Pedro are also among the names to miss out on the latest Spain call-up as preparations begin for the final squad list ahead of the summer tournament in Poland and Ukraine.
Barca dominate the list with eight players, followed by Madrid and Athletic Bilbao, who each have four men in the squad.
Spain have been drawn with Italy, Republic of Ireland and Croatia in the Euro 2012 group stage.
The squad in full:
|Sergio Ramos||Real Madrid|
|Andoni Iraola||Athletic Bilbao|
|Javi Martinez||Athletic Bilbao|
|Xabi Alonso||Real Madrid
|Iker Muniain||Athletic Bilbao|
|Fernando Llorente||Athletic Bilbao|