A Carlos Tevez penalty earned a point for the Premier League champions and Mancini believes that recent fixtures have caught up with his squad.
The Italian said: "It was a hard game. In the first half we went down and it was difficult, like every game against Everton.
"We tried to break them down but this week we have played three games in six days so we are tired. We also have players injured."
City have moved to the top of the Premier League following the result.