Warren Gatland reckons Andrew Porter deserves a "huge kick up the backside" from Andy Farrell after dodging a yellow card in Cardiff.
Ireland prop Porter made a brilliant try-saving tackle on Jac Morgan in the first half.
But Gatland believes the Leinster man could have been sin-binned for a late tackle on Liam Williams as the Wales full-back scored his side's only try in the 34-10 defeat to Ireland.
"I’m not sure Andrew Porter needed to do that because he was clearly scoring the try," said the Wales boss.
“With Porter, if I was his coach I would give him a huge kick up backside because even though he’s made a great tackle on the line to hold up Jac Morgan, he probably needs a reminder that in a big game, those things are potentially a yellow card (the tackle on Williams)."
Gatland said he was "comfortable" with ref Karl Dickson's decisions but added that Ireland replacements Iain Henderson and Bundee Aki could also have been sin-binned.
Henderson collided with Williams as he attempted to block down the out-half's kick, while Aki was penalised for an off the ball tackle on George North.
In fact, only one player was shown a yellow card in the Six Nations opener - Williams.
"I thought the tackle on George North, he was tackled off the ball, was potentially a yellow card because it was a good attacking position and he doesn’t have the chance to clear out," said Gatland.
"Iain’s gone up there and you could argue he could have got his body out of the way.
“I’m not sure. There’s a lot worse, they weren’t massive incidents.
"I’m comfortable with the ref, there have been times with yellow cards that they are given away too freely.
"I felt in that first-half there were a couple of times we could have got over the line and we've had an intercept of seven points against us. Potentially it could have been a lot closer.
"I felt in the second-half when we were putting Ireland under pressure at 27-10 if we'd scored then and got it to 27-17 it could have been an interesting couple of minutes.
"They are a very good side, the number one side in the world, and they showed that this afternoon."
Wales skipper Ken Owens added: "It was tough. We didn't deliver on what we spoke about.
"They didn't do anything that really surprised us. They got on top of us and with our discipline we gave them entries.
"I'm proud of the boys. We stuck at it and the boys left everything out on the field.
"There was plenty of experience out there. I thought we took some good decisions, some brave decisions and just lacked a bit of accuracy, myself included, at lineout time.
"At first phase we turned the ball over and put ourselves under pressure. That's the ball game, that's probably the difference between us at the moment and a team like Ireland who are number one in the world.
"They are just accurate, clinical and got the job done. I thought we created enough but lacked that accuracy.
"From the effort we asked from the players for 80 minutes we delivered that. I can't question that at all.
"It's that small detail, that little bit of accuracy, and that detail which let us down."
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