It was the third hat-trick of Tevez's career at Eastlands and came on his 27th birthday.
Platt said: "We pushed players on in the first half. We knew that when we played at the Hawthorns our full-backs played in their half.
"The manager (Roberto Mancini) reinforced that before the game. We wanted to play in their half when we had the ball.
"We almost had numerical advantage going forward which enabled players like Carlos and David Silva to come off and find little holes. Carlos has also hit the post as well."
However, Platt was unhappy they did not kick on.
He said: "We were a bit disappointed at full-time we have not gone on and got more goals and played in a way we did in the first half.
"The next goal would have been very important because if they get it they are right back in it and they had a few opportunities.
"We have kept a clean sheet and that is a bonus. It is important for Joe Hart and his defenders. But what really counts is that we secured the three points."