Miroslav Stoch struck an 87th-minute winner to condemn the reigning European champions to defeat in Zilina on Thursday.
The result comes months after Spain suffered a group-stage exit in a tame defence of their World Cup crown in Brazil, and Del Bosque admits that criticism is inevitable.
"I fully understand this criticism," he told reporters.
"However I'd like to ask for some respect from the point of view of that this is sport. I haven't ever called anybody to retract anything and I never will.
"We have to accept some criticism based on certain results and as we haven't won the last fixtures."
Del Bosque's side should get back to winning ways when they travel away to Luxembourg on Tuesday.