Neil Warnock felt Cardiff were denied a "certain penalty" in their 2-1 home defeat to Burnley on Sunday.
Cardiff had the better of the first half but saw appeals for a penalty waved away just before the break when the ball hit Matt Lowton's arm from Callum Paterson's overhead kick.
Burnley then scored twice in the second half, either side of a strike from Josh Murphy, to leave Cardiff winless after seven matches in the Premier League.
Cardiff 1-2 Burnley
As it happened
Reflecting on the penalty decision, Warnock said: "His hand is up there and it's unnatural, it's a penalty, but we don't get them as a smaller club. I don't know why because I thought it was a certain penalty and that would have changed the game.
"The fourth official said his hands were in a difficult place to see. But sometimes it depends what referee you get. The referee gave it yesterday [in Leicester's win at Newcastle], but today he didn't."
Despite the result, Warnock said he could not fault his players as they had 19 shots compared to three from Burnley and largely controlled the game.
"I thought we were the best side all the way through," said Warnock. "We had to work really hard to lose it. Obviously the two goals were the difference but I thought we were super in everything we did apart from the two goals, they were quite simple and we should do better.
"On another day we would have won quite easily but it wasn't to be. We should have taken advantage of the opportunities we had. We just have to get the rub of green and I don't think we did today."