Lopez has been first-choice goalkeeper under head coach Carlo Ancelotti this season, restricting Casillas to 15 starts in the Copa del Rey and UEFA Champions League.
The 32-year-old has no complaints about Ancelotti's decision and insists Lopez's 10 clean sheets in 2013-14, coupled with only conceding an average of a goal a game, validate the Italian's team selection.
"So far, the gaffer has opted for Diego Lopez in La Liga and we are leaders thanks in no small part to his efforts," Casillas told Marca. "I, when I play, try to do the best I can.
"You have to follow the manager's orders.
"Of course, everyone wants more minutes.
"I, at this moment, as I said, respect the manager's decision, and if he says cup and Champions League, I'm happy with that and (will) try to do my best for the team."
Despite a lack of first-team action, Casillas remains Spain number one ahead of the FIFA World Cup, but he insists his focus is solely on helping Madrid win trophies and will only turn his attentions to the tournament in Brazil at the end of the season.
"We have four months remaining until we the World Cup, the reality now is the club," he added.
"If we do well and get the tenth (Champions League title), many players in the squad will be in the World Cup (but) currently have to think about the club."
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