Ireland head coach Joe Schmidt criticised referee Jaco Peyper after a 10-9 defeat to France in the Six Nations.
After beginning their campaign with a 16-16 draw against Wales, Ireland's hope of defending their title took a huge blow with Maxime Medard's converted try consigning them to the narrowest of defeats in Paris on Saturday.
Their misery was compounded by injuries to Sean O'Brien, Dave Kearney, Mike McCarthy and Jonny Sexton, with the latter the victim of a late shoulder charge from Yoann Maestri in the first half.
And Schmidt felt Peyper could have done more to protect his players.
"We're disappointed there wasn't more action taken for things that happened off the ball. I'm not sure but we'll review those," Schmidt told RTE. "When there was a double-up of foul play, it was disappointing that it wasn't sanctioned.
"We felt a stronger performance from some referees might have determined that [yellow cards were issued], but you have to stay in the game and determine the outcome and not rely on someone in the middle."
Schmidt also felt aggrieved that the television match official was not called upon after a try for Dave Kearney was ruled out for a knock on by Robbie Henshaw, although the replays proved it to be an incorrect decision.
"I think the first time Dave Kearney went over carrying the ball, the ball has ricocheted off Robbie Henshaw's chest or stomach, so there is no knock-on," he added.
"In a try scoring action, I felt it warranted having a look, but unfortunately that wasn't the case. We don't have control of the TMO, so we have just got to be more efficient when we get into the 22."
Ireland captain Rory Best was frustrated by the nature of the defeat, and believes defending their title may now be too big of an ask.
"It makes it very hard [to defend the title] obviously now having no wins in the first two games," he told the BBC.
"I think we'll have to re-assess, but for us in that second half we just couldn't quite get the dominance that we had in the first half. From our point of view we'll look at this as a massive missed opportunity."