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Lancaster's England side crashed out of their home World Cup in the group stages in 2015

Champions Cup final: Leinster v Racing 92 Venue: San Mames Stadium, Bilbao Date: Saturday, 12 May Kick-off: 16:45 BST Coverage: Live commentary on Radio 5 live and online, plus live text coverage on BBC Sport website and app

Few people can attest to the fickle nature of top-level sport like Stuart Lancaster.

For much of his near four-year spell as England head coach, Lancaster was lauded for his diligence and vision, before a disastrous World Cup in 2015 resulted in his sacking and left his reputation in pieces.

Closure wasn't immediately forthcoming; Lancaster spent months travelling the rugby world, gaining experience and broadening his horizons, but the right job eluded him. Either he didn't want them or they didn't want him.

It wasn't until September 2016 - almost a year on from his darkest hour - that Lancaster returned to full-time coaching, as the unusually titled 'senior coach' at Leinster, working with head coach Leo Cullen.

Now in his second season with the province, respect for Lancaster across the Irish Sea continues to soar, with his side on the verge of a historic Champions Cup triumph.

Victory against Racing 92 in Saturday's final in Bilbao would seal a fourth European Cup for Leinster, equalling the record of French giants Toulouse.

And those who have seen his work first-hand in Dublin are in no doubt as to Lancaster's influence. Along with Cullen, he has helped transform the Irish side into the dominant force in European rugby.

'Revolutionised training'

With Lancaster on the touchline, Leinster are aiming for a record-equalling fourth European title on Saturday

"He's been a massive, massive addition to the squad," Ireland and Leinster great Jamie Heaslip told the Rugby Union Weekly podcast.

"He has definitely brought a really good intensity and structure to training and he's been a massive addition in terms of playing, and behind the scenes in terms of culture."

Flanker Dan Leavy, one of a handful of young Leinster players developed by Lancaster and now making hay for club and country, is similarly convinced.

"Stuart revolutionised training through the standards he set. We are blessed with the coaches we have here," Leavy said.

"He is loved and adored in Leinster. I would put him up there with Joe Schmidt," adds Heaslip, in another ringing endorsement.

"It's not about screaming and shouting," former Leinster winger Shane Horgan told the Matt Dawson Rugby Show.

"Top-class players want in-depth detail and that is what he is providing."

Liberated as a number two

Lancaster appears liberated at Leinster; he is free from English rugby and the inevitable baggage that comes with it, while his current role has also allowed him to return to his roots - coaching players - after struggling to prioritise towards the end of his England tenure.

"He's always been a great coach," says England scrum-half Danny Care, whose involvement with Lancaster goes back almost two decades.

"We go back to when I was 14 or 15, and we would do private one-one-one passing sessions when we would be soaking the ball in washing-up liquid.

Danny Care worked with Lancaster at Leeds early in his career

"I think Stuart is relishing not being the number one man, and he can go and do what he's really good at, which is coaching rugby."

"He has said that when he was with England he was 20% coaching and 80% management and with Leinster that has been flipped on itself," added Horgan.

"He ended up giving presentations and power points rather than coaching sessions. He got it the wrong way round," World Cup winning fly-half Paul Grayson told the Matt Dawson Rugby Show.

"Leinster is a great place for him. You don't have to establish a culture - you are three-time European Cup winners."

The steel forged in crisis

While Lancaster's experiences with England cut him deeply, it is only through those dark times that he has emerged a better coach, according to Grayson.

"He got the wrong job at the wrong time, but it was only by getting that job that he got the Leinster role," Grayson explained.

"There is not a cat in hell's chance that an England development coach gets that sort of role.

"He is redeeming himself, but he is learning, doing it the right way, and adding value to himself."

Ireland beckons?

While Horgan believes he is "suited to being a number two", Lancaster continues to be linked with a number of top club jobs in England, forcing him to pledge his commitment to Leinster for the foreseeable future.

But such has been his impact in Ireland, sources have indicated he could be in the conversation for a role in the national set-up down the line, possibly working with current Ireland defence coach Andy Farrell.

Victory in Spain on Saturday would do his chances of a sensational return to the international scene no harm whatsoever.