Martyn Williams has called for the Welsh Rugby Union to offer defence coach Shaun Edwards a new contract.
Edwards' deal ends after the World Cup in October, and the former GB Rugby League international hinted Saturday's 23-16 victory over Ireland could be his last with Wales in the Six Nations.
Wales made a tournament record 250 tackles against Ireland.
"It would be a huge loss if he does leave. I hope the WRU sign him up quickly," said Williams.
"Having worked under Shaun for quite a few years he is without doubt the best defensive coach I have ever worked with, he's so meticulous about every little detail.
"Ireland tried a few fancy plays but you could tell just how well-coached the Welsh players were. They knew what was coming and that's massively down to Shaun."
Edwards was brought in to the Wales set-up on a part-time basis by Warren Gatland when the New Zealander was appointed head coach in the autumn of 2007.
The pair had worked together at London Wasps, where Edwards remained until taking up a full-time appointment with Wales in 2011.
Wales won Six Nations Grand Slams in 2008 and 2012, and also won the title in 2013, when they did not concede a try in consecutive matches against England, France Italy and England.
And in the 2008 campaign Wales conceded just two tries in the entire tournament.
"Under Warren Gatland what's been the strongest part of our game? Defence, there's no doubt," Williams told BBC Radio Wales.
"That's what took us to three championships. So if Shaun is out of contract it will be a huge blow if he does leave.