The Manchester City winger scored in stoppage time as Spain snatched a 2-2 friendly draw in Chile.
Eduardo Vargas had put Chile ahead twice in the match, but equalisers from Roberto Soldado and Navas earned Spain a point.
Del Bosque was aware how difficult winning in Chile would be and praised the influence of Navas, who came off the bench early in the second half.
"It was a tough one. A very difficult match, which we knew would be intense," Del Bosque said.
"Chile were hurting us, but the entrance of Navas was the answer for us."
Navas, who replaced Xavi when he side were 2-1 down, said that Spain's 2-0 FIFA World Cup qualifying win over Finland on Friday was more important.
But he was pleased with the fight his side showed, as they rounded off a good week with a fighting point.
"The important thing though was that we beat Finland last Friday and that's what we managed to do," Navas said.
"We knew what Chile were going to be like," he continued.
"We knew they would have a great attitude going into this game."
Spain lead Group I on goal difference from France, having played one match less than Didier Deschamps' side.
Spain will finish their qualifying campaign with home fixtures against Belarus and Georgia.
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