REPLACING Brian O'Driscoll and Gordon D'Arcy will be Joe Schmidt's toughest challenge as Ireland boss, according to Peter Stringer.
Former Ireland scrum-half Stringer believes O'Driscoll took a "brave" decision to retire this summer and reject an assault on Rugby World Cup 2015.
Bath half-back Stringer hailed O'Driscoll for a "typically selfless" move to turn down a tilt towards a fifth World Cup campaign.
Stringer has no doubt O'Driscoll would have featured prominently in Ireland's 2015 drive had he pushed his glittering 15-year international career that bit further.
Ireland's 34-year-old centre D'Arcy will play on past the summer, but ex-Munster star Stringer believes the duo will leave a huge chasm once both exit the international arena.
"It will be a huge challenge to take it on again," Stringer said.
"But in the last few years that core group has started to thin, with guys like Jerry Flannery, Marcus Horan, Ronan O'Gara, John Hayes, all retiring.
"People were always looking then, saying what are Ireland going to do now, but already they've taken it on to another level with the guys who have stepped in.
"Joe's influence is massive, from what I hear, coming from Paul (O'Connell) and Brian, the guy's attention to detail is second to none. The quality of coach Ireland have now is top class, and he's bringing young guys through quickly too.
"The young guys on the fringes, they will hopefully step up to the mark and things look pretty good for the future.
"Trying to find people that will fill those boots is the next big step within the Irish structure, given they've been there for so long and worked so well together, both at provincial and international level.
"I'm sure Brian will be passing on everything he can. But that will be a vital area for them once both those guys do go.
"I think it makes it an even braver, an even stronger call, to retire at this point."