Paul Lambert believes inconsistent performances form referees is beginning to affect the results of his Aston Villa side.
Villa have seen three players sent off in their past four matches which has coincided with a four-game winless streak.
Fabian Delph was the most recent to be given his marching orders, in Sunday's 0-0 draw with Sunderland, and according to Lambert the form of the referees is taking its toll on the West Midlands club.
"You've seen a lot of challenges in recent games - some real bad ones as well - and there's been yellow cards," said Lambert.
"I think it is an inconsistency thing which annoys me the most. I can only speak for ourselves.
"We are sometimes an easy target because we are a youngish side and I think that can go against us. The referees have got a hard job but last year I don't think we got a red card at all.
"We have to play with commitment and drive and I don't want to curtail that, but there has to be common sense as well."
13th-placed Villa, who have taken 21 points from 19 matches, next take on Crystal Palace at Villa Park on New Year's Day.
