Rival boss Lee Johnson claims the goal that set Sheffield Wednesday on their way to victory at Bristol City should never have been allowed to stand.
The 2-1 win catapulted the Owls into the Championship play-off places as they head into the international break.
But Johnson pointed the finger at the match officials after seeing his side downed by two Lucas Joao goals in the second half.
Joao struck in the 64th minute and added a second two minutes later before the Robins converted a 77th-minute penalty.
The Robins manager said: "I have watched the first goal again and it was three yards offside. We knew that at the time and it is so frustrating.
"The first goal in Championship games is so important and today we have conceded it through sub-standard officiating.
"Every day we work with our defenders on squeezing up to get our high press going. An individual has let us down today and it wasn't one of my players.
"I don't normally talk about officials, but today it was such a key moment. I think they knew immediately that an error had been made."
Wednesday, who have lost only once in their last nine league outings, leapfrogged the Robins to move into sixth spot.
Jos Luhukay's side struggled in the opening period before picking up the pace in the second half, leaving Johnson to bemoan his team's missed opportunities as he took another swipe at referee Andy Davies.
"We also have to look at the fact that we failed to take some great chances," he said. "But it was a game that could have gone either way and this sort of thing has to stop at our level.
"I thought we played some great stuff at times. We dominated the first half and, while the second was closer, we might easily have won."
The only downside for the Owls were injuries suffered by Steven Fletcher, Jordan Thorniley and Barry Bannan.