Platt admitted City had been tempted to substitute striker Balotelli at half-time after he had been booked early on for bringing down Claudio Yacob.
Referee Mark Clattenburg then spoke to City captain Vincent Kompany after Balotelli escaped a second yellow card for a challenge on Shane Long.
Platt said: "The temptation is there (to substitute Balotelli). He got booked inside 20 minutes.
"We looked at it at half-time but he was causing them a problem and we felt confident just by speaking to him that there was not going to be any loss of head. He looked pretty calm."