Eddie O'Sullivan has concerns about the referee for Ireland's game with New Zealand.
His comments follow Ireland vice-captain Johnny Sexton saying the national team has "come on the wrong side of Wayne Barnes in the past".
O'Sullivan is worried about the effect Barnes could have on the crucial game saying the English referee's Achilles heel is that he can lose control when a game gets frantic.
"If the game turns into a very fast paced, very physical games, as is probably likely to be - I think he could struggle. He seems to lose his composure" said the ex-Ireland boss, speaking to Off The Ball.
"He's very good on the law. He understands the law very well, he's a barrister by trade... But I think at times, certain games, he gets a bit flustered."
"He can be very whistle happy and make very harsh calls. And I think that could be a problem on Saturday if the game opens up and it's very frantic and there is a lot of physicality.
"If there is an edge to it then and there are a couple of late hits or something, you know these games can bubble right on the edge. I think it wouldn't be the best place for him to be. So it's about managing that really.
"Ireland are probably throwing it out there as well. That message will get to him that we know that he penalises us more than any other referee, so keep that in mind before you blow the whistle.
"That's a bit of tactical flair there by Joe Schmidt to get that out there. Which is fair enough. That's what you do."
Sexton told the media yesterday that his side must stay on the right side of Barnes on Saturday.
"We have to look hard at our discipline because you can’t give away too many penalties against the All Blacks. If you look over the years, we’ve given a lot of penalties away with him (Barnes). We need to figure out why and rectify that," Sexton said.
"We pride ourselves on our discipline. We are coached to be as disciplined as we can be. We will look at a game and after the game we will get, not in trouble but it will be highlighted where we could have given away penalties.
"So our discipline, on a list of importance, is up there. We’ve come on the wrong side of Wayne Barnes in the past so it’s something we’re going to have to look at even more so this week."
Ireland take on New Zealand at the Aviva Stadium in Dublin on Saturday with kick-off at 7pm.
- additional reporting by Irish Examiner