Newport Gwent Dragons director of rugby Lyn Jones criticised the referee for giving "needless" yellow cards in the 32-13 Pro12 loss to Edinburgh.
Props Boris Stankovich and Phil Price, fly-half Dorian Jones and flanker Nic Cudd were sin-binned by Marius Mitrea in the second half in Murrayfield.
Jones was particularly incensed by the cards shown to props Stankovich and Price for scrum infringements.
"There's no need for those yellow cards at all, it's unnecessary," he said.
"That's what we've got to deal with."
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Stankovich was the first to go after Italian referee Mitrea lost patience as the penalty count continued to mount in the scrums.
Replacement prop Price joined him in the bin as the Dragons scrum crumbled under more pressure, leading to uncontested scrums for a period.
"They had a good scrum, fair play, on that one occasion and that split us. That's fine, it's a fair penalty. But it's not a yellow card [for Stankovich]," Jones added.
"Neither is Phil Price a yellow card. No way is it a yellow card."
Fly-half Jones received the third yellow card for a tip tackle and flanker Nic Cudd followed for being offside near his own tryline.
Coach Jones said the Dragons will be making their feelings known about the referee's performance to the Pro12 officials.
"We just want to make sure things like that don't happen again," the coach added.
"There are lines involved we need to follow and we certainly will be following them up."