Los Blancos recorded a narrow 1-0 win over Granada on Monday night thanks to a Karim Benzema goal in the first half, but the major talking point was again the decision to leave Casillas on the bench.
The Spain No.1 was discarded by Jose Mourinho at the Santiago Bernabeu last season and though many expected him to reclaim his starting berth under Ancelotti this term, the Italian has so far opted to stick with Lopez - a decision he was happy to stand by after the match.
He told reporters after the game: "Diego Lopez played the first game and now he has played the second game.
"He is playing well at the moment. There is nothing more. The pressure is fuel to me (regarding the focus on the decision)."
Monday's victory was their second in as many league outings and Ancelotti reserved special praise for Benzema's goalscoring start to the season after grinding out the three points.
"Benzema is playing well and scoring. He has started well in the league," he added.
"The team was balanced. Luka Modric and Isco played well. Isco had to sacrifice a bit because he can attack more. The work of Di Maria was also important."
The former Paris Saint-Germain boss, who only took over the reins in the Spanish capital over the summer, then revealed he had observed Barcelona's narrow win over Malaga with interest.
Ancelotti added: "I saw the Barcelona match and it was also difficult for them. At the moment the most important thing is to get points and work for the short term."
Madrid are next in action on Friday when they host Athletic Bilbao.
