The defeat leaves Real third in La Liga, three points behind leaders Atletico Madrid, but Ancelotti elected to remain optimistic when speaking after the game.
"I don't think we deserved to lose," the Italian told members of the press. "We created many opportunities but we didn't prepare well enough for Sevilla.
"Their first goal was an error and it made things hard for us. We're behind right now, but it's not impossible."
Ancelotti's side will look to recover from successive defeats when they host Rayo Vallecano on Saturday night.