Joe Schmidt was unhappy with Australian referee Angus Gardner after Ireland's shock 19-12 loss to Japan, saying he could understand why his players might feel "frustrated" at the penalty count.
Ireland conceded nine penalties to Japan's six, with Schmidt noting it was "not too dissimilar from the last time we had this referee".
However, the Kiwi-born coach — who defended his decision to name an unchanged pack six days after their last game — called the Brave Blossoms as a "real handful" and acknowledged that they had played with "intensity, skill and energy throughout".
"Japan did not exceed my expectations," Schmidt said. "Unfortunately, they met them. They showed intensity, skill and energy throughout. We controlled the first quarter when we scored two good tries but after that we struggled to contain them. The defeat is tough for us to take but we have to roll up our sleeves and prepare for Russia [in Kobe on Thursday]."
On the refereeing, Schmidt added: "We'll go back and have a look at it. I certainly understand the frustrations of some of the players and in discussing things with them, based on what I saw on the monitor, it's not too dissimilar from the last time we had this referee.