Torres blew hot and cold with his club Chelsea last season but looked lively for the world and European champions against the South Americans in Seville. (Agencies)
He capped his evening's work with a well-taken penalty six minutes into the second half before making way for Cesc Fabregas on the hour.
"We have a lot of confidence in him and that's why he is here," Del Bosque, who is due to announce his final squad for the tournament in Brazil on Saturday, told a news conference.
"We are pleased with how he worked tonight," he added.
Torres, who netted his 37th goal in 107 appearances for Spain, is hoping to play a part in what would be his third World Cup after Germany 2006 and South Africa 2010, when he helped the Iberian nation win their maiden world title.
The 30-year-old is vying for a place with Diego Costa, who has been suffering with a series of niggling injuries in recent weeks, Fernando Llorente, David Villa and Alvaro Negredo.
Del Bosque also suggested Manchester City winger Jesus Navas was unlikely to be on the flight to Brazil after missing the final part of the Premier League season with an ankle injury.
"Jesus Navas has been recovering well these past few days but the reality is he has not played for two months and we prefer to have someone in good shape," Del Bosque said.
"He is not ruled out completely but it will be hard for him to make it," he added.
Sevilla left back Alberto Moreno and Athletic Bilbao midfielder Ander Iturraspe, who played against Bolivia on Friday, would not be in the final squad, Del Bosque said.
Spain, whose final warm-up match is against El Salvador in Washington DC on June 7, has been drawn in Group B at the World Cup finals with Netherlands, Chile and Australia.
Their first game is against the Dutch on June 13, a repeat of the 2010 final which Spain won 1-0 after extra time.
Torres blew hot and cold with his club Chelsea last season but looked lively for the world and European champions against the South Americans in Seville.