The Spain boss has hit out at the Real Madrid goalkeeper's critics but refused to be drawn on whether the Roja captain or Diego Lopez should start for the club
The Blancos shot-stopper suffered a hand injury in January which kept him sidelined until late March but he has been prevented from making a first-team comeback due to Diego Lopez's form in La Liga, the Champions League and the Copa del Rey since his arrival from Sevilla.
Although Del Bosque refused to be drawn on the debate over who should be handed the No.1 spot for Jose Mourinho's side, he does believe the World Cup-winning captain deserves more respect from his detractors.
"We know he is a legend in Spanish football, nobody has done what he has, but suddenly he is in an uncomfortable situation," Del Bosque was quoted as saying by Marca.
"[Whether he plays] is a decision for the coaches and the club. I won't say a word on the matter, you won't even get a smile from me on it. It's not a trivial matter because you have to respect the club and his coach and I don't want to cause problems with anybody.
"I don't think they would have questioned [Peter] Shilton in England in the same situation or other players who have been legends in their national teams".
Casillas' lack of game-time in 2013 raises questions as to whether he will feature in the Confederations Cup for Spain in the summer, but Del Bosque hinted that he would be picked regardless of whether he returns to the Madrid first team.
"The important thing is he is back from injury, that he is training and we have enough time ahead of us to make decisions [before the Confederations Cup]," the Roja coach continued.
"What I must say is he is our player, he is one of the best to have played for us in over 140 matches and we're very fond of him so the most logical thing is to have him with us."