Ancelotti's job is in serious doubt after losing ground to Barcelona in the LaLiga title race and also their elimination from the Champions League.
But Capello told Telemadrid: "I hope they don't fire Ancelotti and that they show him the same respect he has for Real Madrid.
"I see Madrid suffering, with Carlo, the president and the fans. It was a strange match against Arsenal. It didn't seem like a normal Madrid to me, with their usual determination. The opponent played a good match. Carlo is the most successful coach in the world , but he can't always solve problems.
"This year he's had a lot, with many injuries , having to build a defence in every game, and he's missing a conductor like (Toni) Kroos in midfield. It was very noticeable. That's where the game and the filter for defending are born. He's the heart of the team."
On the title race, Capello added: "I think Barcelona will be champions this year because they score a lot of goals. On Saturday they were lucky because they got a penalty in the 98th minute, but to win you need luck."