Peter O'Mahony has played down his "heat of the moment" reaction to Tomas Lavanini’s cheap shot on Cian Healy.

The Pumas second row was red-carded in the 60th minute of Ireland's comprehensive 53-7 victory at Lansdowne Road.

Healy, who scored a try on his 112th cap, was caught in a ruck when the Clermont second row launched himself into the replacement prop, making contact with his head.

It was the 28-year-old's third red card in 68 internationals.

"You're a scumbag, you knew exactly what you were doing, you think you're a hard man? watch yourself," was the stand-in captain's initial response to the dangerous challenge on his team-mate.

Referee Matthew Carley saw it that way too and dismissed the Argentina lock.

"Ah look, it’s heat of the moment stuff," said a relaxed O'Mahony in the post-match press conference.

"I’ve been on the other side of that as well so it’s a split-second decision from his point of view. Ah look, there isn’t much to be said about it now.

"These things happen. He’s trying to make an effort to clean someone out and he’s got it wrong. That’s what I thought at the time and you’re trying to look after your buddies, looking after your mates and the last thing you want is for them to get injured.

"From his point of view it’s tough as well. It’s literally fractions of a second and at the time I was pissed off."

Former Lions captain O'Mahony was himself sent off during last spring's Six Nations clash with Wales, a game which Ireland went on to lose.

"I’ve been on the other side of it and you’re talking about hundredths of seconds where pictures change and, you know, red card," added the 32-year-old.

"The disappointment of getting a red card for your country is nothing you can experience, I wouldn’t wish that on anyone."

Meanwhile, Tadhg Beirne, who ended up starting as a late replacement for Iain Henderson, who injured his hamstring in the warm-up, reckons the team, who added the Pumas scalp to that of Japan and New Zealand in the Autumn Nations Series, are headed in the right direction.

"We’re building and we want to keep building and this time last year we knew we were on the way to something and things weren’t clicking at times," said the Munster forward, who scored his sixth try for Ireland.

"Even out there today, things weren’t clicking 100%, especially in the first half, we were scrappy at times and when that happens we need to look at that.

"We want to keep striving to get better and make sure that the way we play is an incredibly difficult way to stop our performances. I think we are on the way there but we still have a long way to go."