After returning from knee surgery shortly before the tournament, Torres was overshadowed by strike partner David Villa in the European champions' three Group H matches and looks well short of his devastating best.
While Villa netted three times, including two of the finest goals so far in South Africa, Torres squandered several chances and looked a shadow of the player who scored a brilliant winning goal in the Euro 2008 final against Germany.
"It's not easy coming back after an operation," the 26-year-old said in an interview with Spanish radio on Saturday.
"I think I still have a little way to go before I am back at 100 percent, although I am close," he added.
"The main thing is that he played in the three (group) matches, he has been making progress in his preparation and he is better," Del Bosque told reporters on Saturday.
"He may not have scored but he helps us by being a menace for the opposition's defence," he added. "And when he gets into space he is always a very dangerous player."
Spain and Portugal, who have never met at a finals, know the winners at Cape Town's Green Point Stadium will avoid the big guns with Paraguay or Japan waiting in the last eight.
Midfielder Deco has recovered from the hip problem that ruled him out of Portugal's final two Group G games and Spain central defender Raul Albiol, who has been an unused substitute thus far, is sidelined after being injured in training.
Midfielder Javi Martinez, who would likely replace Alonso in Spain's starting lineup, also jumped to Torres's defence.
"Fernando has been bringing a lot to the team," the 21-year-old, who was a surprise inclusion in the squad and has made only three appearances for the European champions, told a news conference on Sunday.
"The space he opens up is fantastic for us and I am sure he will rediscover his top form in the next few matches."
