Although the Spanish exerted their customary dominance at Wembley against a depleted and defence-minded England they were unable to convert long periods of possession into goals and the hosts grabbed the winner when Darren Bent nodded a James Milner free-kick on to a post and Frank Lampard followed up to score.
The defeat was the latest reverse against heavyweight opposition for the Spanish since they lifted their first World Cup in South Africa last year following friendly losses to Argentina, Portugal and Italy.
"We analysed what happened," Del Bosque told a news conference ahead of Spain's match against Costa Rica in San Jose on Tuesday.
"We had some good possession and practically kept the ball from them," added the former Real Madrid coach.
"We did not have necessary finesse playing the final ball but everything else we did pretty well and we therefore shouldn't alarm ourselves, although we should not ignore it either."
Spain's relatively poor run in friendlies contrasts with their perfect record of eight wins in eight in qualifying for Euro 2012, when they will seek to defend their continental crown.
They have not lost a competitive game since slipping to a shock 1-0 defeat by Switzerland in their opening match at the 2010 World Cup and will be strong favourites to win a third successive major tournament in Ukraine and Poland next year.
POWERFUL STRIKERS
Del Bosque said his squad contained enough depth to allow him to respond to most situations.
He opted to play without a traditional target man on Saturday, deploying forward David Villa and playmakers David Silva and Andres Iniesta in attack and leaving powerful strikers Fernando Torres and Fernando Llorente on the bench.
"The richness of a team depends on its variants," said Del Bosque who brought on Torres in the second half.
"We have various ways of playing depending on which players we pick.
"The playing concept does not vary but there are alternatives. We must not blindly stick to one way of playing, there is not only one system, one scheme.
"You have to prepare yourself for every situation."
Del Bosque's words were echoed by midfielder Cesc Fabregas, who squandered a decent late chance for an equaliser against England on his return to London.
"We have to adapt to everything because this can happen to us," the former Arsenal captain said.
"Despite the lack of goals, we controlled the game well and our attitude was good," he added.
"There is little to criticise about the attitude and the performance but football is like that.
"Sometimes things happen that you are not expecting. They scored from a free kick and we lost."
Costa Rica, ranked 62nd in the world, come into Tuesday's game having lost 2-0 in a friendly in Panama last week.
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