Bruce has been heavily criticised just seven games into his first season at the club, but Allardyce is having none of it.
"Steve will be sleeping very restlessly at the moment," he told talkSPORT.
“It is going to be a tough one up to maybe Christmas.
“But, in saying that, we have got to look at the situation and say he has got more points than Rafa had this time last year.
“I still don't know why Steve is getting stick. Rafa didn't get stick but Steve is. I just don't understand it."
On the thrashing by Leicester City, he continued: “To blame Bruce just yet is a long way off as he has only just arrived.
“They did go down to ten men with a tackle that would have been perfectly legal in our day.
“He played the ball but his momentum carries him straight through into the opposition player and everyone calls that one reckless.
“I would like to know how you do that tackle. He couldn't stand on his feet because he was too far away.
“I understand he catches the lad as he goes through the ball and we don't want to see players injured but it is very difficult to make that decision.
“In the end, it is how they capitulated. Down to ten men it is very difficult but they should have put up a better defensive performance."