According to the new rules, the match officials are now under orders to penalise shirt-tugging and blocking, which the Foxes were able to get around last term.
Leicester lost 4-1 to Manchester United on Saturday, and three of the Red Devils goals came from corners with Simpson insisting that the new rules have left the Foxes vulnerable at dead ball situations.
"Err, I have to be careful what I say," he said.
"It is in your mind, yes, we have seen a few decisions this season. It is in your mind.
"It is something we have to learn to adapt to as players. They have changed the rules.
"The way it was last season, I thought we were very good at defending set-pieces and we made it tough for the opponents.
"You have been doing that for all your career and suddenly you have got to change it, but it's the same for everyone, it's something we have got to work on and look at."