Are you surprised? PED are no doubt being used as well. These are incredibly competitive people that have to win. They like anyone else will do whatever it takes to win.
It was 0-0 v Watford. We were looking for a goal to win it and therefore that substitution made sense at the time. Murphy today was the right choice. If we were one down or it had been 0-0. We'd probably have seen Izquierdo on.