The European Champions defeated Belgium 5-0 in La Coruna on Saturday to maintain their six-point advantage over Bosnia-Herzegovina at the top of Group 5.
With three qualifiers still to play, Vincente Del Bosque's men are still not guaranteed top spot. "It seems incredible that we are not yet qualified," Liverpool striker Torres told a press conference.
Spain could secure qualification with victory over Estonia in Merida on Wednesday, though, provided Bosnia-Herzegovina do not beat Turkey the same day. Even a draw could be enough if Bosnia-Herzegovina lose.
Their 2-0 defeat to the USA in the semi-finals of the FIFA Confederations Cup in June is their only defeat in almost three years, but Torres believes the team have not yet reached their peak. "We hope that our best has not come yet," he said. "We want to improve, keep winning and getting better as a team, adapting to different systems."
Before losing to the United States, Spain had racked up a world record 15 wins in a row. Midfielder Albert Riera, a club-mate of Torres at Anfield, is unwilling to call the current team the best Spanish side ever. "We are doing important things and breaking records," he said. "But each selection has its stage, I do not like saying it is the best."
The Spanish FA said defender Gerard Pique, who scored against Belgium, has recovered from a shoulder injury and trained normally on Monday. Right-back Alvaro Arbeloa is also expecting to be fit to face Estonia, despite picking up a foot injury against the Belgians.