Silva's blistering start to the season had critics hailing his contribution and put his name up as a potential player of the year candidate.
However, the former Valencia playmaker faded since the turn of the year and struggled to make an impact for City, which coincided with a downturn in terms of goals scored for his side.
Mancini conceded that Silva has been over-utilised by both club and country and is currently playing below standards due to fatigue and it's only normal to expect a drop in standards due to fatigue.
"I don't know how many games David [Silva] has played for us in the Premier League, Champions League, Europa League, Carling Cup, FA Cup plus internationals," he was quoted as saying by The Mirror.
"But it's normal that a player can arrive at a moment when he can't play 100 per cent.
"David always plays here [indicates high level with hand] and now maybe he is here [drops hand lower to chest].
"This is normal, but I hope he can recover."
Silva has been substituted in the last five matches, a sign that his fitness level is not at its peak.