Roberto Mancini's assistant admits that recent battles against Manchester United and Chelsea have taken their toll on the champions, who face Tottenham on Sunday
The after effects of those performances were clearly evident as City laboured to a 1-0 win over struggling Wigan on Wednesday, when they required an inspired Carlos Tevez goal to pick up all three points at the Etihad.
Platt pinpointed mental fatigue as being the key reason for their below-par performance, telling the Independent: "I think we are probably feeling the effects of the two big games we have had, mentally more than anything, what it takes out of you.
"We saw on the pitch we couldn't get anything going. There was a lack of energy about us. Maybe we were mentally tired.
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"We didn't look as though we were going to create anything and I think it needed a flash of brilliance to unblock the game, but that is what we know we have got in the team.
"The physical side is one thing but we can recuperate by fuelling the boys right, getting the right food into them, giving them the right rest and the right cures.
"It is not the physical side that is the problem, but the mental side. That game will have brought us back to earth.
"We will recuperate and go to White Hart Lane."
Regardless of any excuses, Platt was keen to praise Wigan for their performance at the Etihad, and was particularly impressed by their ball retention.
"Wigan are a good team," he continued. "It is probably not the kind of opposition we wanted to face three days after a semi-final - and that coming on the back of the Man Utd game - because they keep the ball, and if you can't get near them because of a lack of energy it gets frustrating.
"It gets frustrating for the crowd, frustrating for the players because normally we have the lion's share of possession here.
"But it was an evening where we had to just get the job done and that is what we have done."
The win over the Latics cut the gap between Roberto Mancini's side and league leaders Manchester United to 13 points, but Platt dismissed any talk of a late title challenge, in spite of City's game in hand.
"It is irrelevant what they do," he concluded. "Unless they open the door completely and have a big collapse then it's over, it's been over for a long time.
"The points gap is far too big. I think they'll get over the line."