Pearson had no complaints about Wes Morgan's early red card, but he felt the Foxes had then done enough to earn a point only to be denied by Alan Dunne's late winner.
"I could bemoan a number of things but I think it's pretty unfortunate tonight," said Pearson, whose side have now gone six matches without a win.
"The players have worked very hard to get something out of the game and to concede a goal so late is, I think, quite cruel. I don't think the players deserve that tonight.
"The players have shown a lot of desire to play in a positive fashion despite going down to 10 men. It's not going for us at the moment but we've got to keep working hard.
"We're not scoring enough goals. We have seven games left and we're losing games by the odd goal. It doesn't mean defeats are any easier to deal with.
"You've got to be careful not to pigeon-hole tonight's performance along with some of our other recent performances; I think we've created some good situations tonight playing with 10 men and still looked pretty dangerous."