Warren Gatland fired a warning to contenders for his British and Irish Lions squad, including England captain Dylan Hartley, that their discipline will be closely monitored during the Six Nations Championship as it will be critical to his side's hopes of beating New Zealand this summer.
Gatland's warning comes in the aftermath of the six-week ban handed out to Hartley for striking Leinster flanker Seán O'Brien during Northampton's Champions' Cup defeat in Franklin's Gardens.
Gatland left those hoping to press their claims for a place in his 35-man squad, which will be announced on April 19, in no doubt that ill-discipline would not be tolerated.
"I like players who play on the edge - particularly going to New Zealand you have to bring the physicality - but discipline is going to be hugely important," said Gatland.
"We can't afford to end up with players getting yellow cards and players missing matches because of suspensions because it will be so costly. That is the message to everyone.
"If you get yellow cards in matches it can be tough to win those games and if it is a red card, it is almost impossible. You don't beat the All Blacks with 14.
"There is a huge amount at stake and a lot of interesting clashes in the Six Nations.
"A lot of players realise it is important for them to do well because individually if they do well and the team do well there is a carrot at the end of it."
Hartley's ban runs until January 23, leaving the 30-year-old just one club match, an Anglo-Welsh Cup game against Leicester, to prove his fitness before England's Six Nations opener against France at Twickenham on February 4.
Asked whether Hartley could not afford another disciplinary issue ahead of the Lions tour, Gatland added: "What Dylan will be disappointed about is that he probably felt that he had put some of the past behind him and I think everyone had thought his discipline record over the last 12 months had been good.
"The captaincy for England has been really good for him.
"It has been an indiscretion that was disappointing."
Hartley's most recent red card was the third of his career and he has now been suspended for a total of 60 weeks.
Hartley was dropped from England's Rugby World Cup squad last year after he headbutted Saracens' Jamie George, but was recalled by Eddie Jones after the Australian had replaced Stuart Lancaster as England head coach.