The Pole was shown a straight red card for a two-footed lunge on Adel Taarabt, leaving Forest a goal down and a man down just midway through the first half.
Boss Billy Davies said: "Him getting sent off was a disaster but credit to the rest of the players for a disciplined, first-class performance.
"He will be fined. What he did was stupid and naive. He will be punished because what he did caused us a problem.
"You try to put old heads on young shoulders and you end up criticising them for naivety - but that is what they are. They are only young players who are still learning.
"Radi is not malicious but he has to learn what it is about at this level."