'McCall has done a brilliant job of creating Saracens' identity'
During his time as England head coach, Stuart Lancaster would have worked very closely with Mark McCall, so he has seen, at first hand, the excellent work that the former Ulster boss has done at Saracens.
Lancaster has been hugely impressed by what McCall has done with the double European champions, and in particular the way that he has helped shape Saracens' identity.
As was the case for the double-header against Exeter Chiefs, who beat Sarries in last year's Premiership final, Lancaster's inside track on the English club will be crucial on Sunday, as he looks to plot Leinster's route to the last four.
Lancaster will be hoping that the returning Grand Slam heroes can add an extra bounce to Leinster at the Aviva this weekend, especially after suffering a poor defeat against the Ospreys.
"I think it'll work both ways," Lancaster said.
"There'll be a spring in the step and the confidence that winning a Grand Slam brings, but that said, every game starts from zero, as we saw last Saturday.
"We had quite a few guys that played in the Grand Slam (match) and we got beaten fair and square by Ospreys.
"It works on the flip side for Saracens, too. Lads will leave a situation where they have not got the outcome they wanted, and the motivation is to go back to the club and play.
"They're a tight-knit group at Saracens. Mark McCall has done a brilliant job at creating that sense of culture and identity that really drives their mentality.
"You saw it in Maro's (Itoje) performance on Saturday against Quins. He got man of the match and deservedly so. So, all this, Maro's tired, I don't buy it. He certainly didn't play tired."
Questions have been asked as to whether or not Saracens are a fading force but that is certainly a dangerous viewpoint to have.
McCall's men are coming to Dublin to prove plenty of doubters wrong, and Lancaster warned against anyone believing that it would be any different.
"I don't think any team goes through the season unbeaten, no team," Leinster's senior coach maintained.
"You have dips along the way. Exeter lost two or three in the Premiership yet went on to win it.
"You learn a lot about yourself when you lose and sometimes it's for the better. I can't say I was pleased with losing against the Ospreys but it certainly gives us plenty of motivation going into this week."
Lancaster also reserved praise for the performances of Dan Leavy throughout the Six Nations, as he really announced his arrival on the international stage.
Back in Leinster, they have known for a while that the flanker was destined for the top, and Lancaster insists that there is more to come from Leavy.
"I've always thought he was going to be there or thereabouts for Ireland, in terms of his quality. When he finally got his opportunity, I think he demonstrated the type of player that he is.
"He's very good over the ball, incredibly strong and powerful, and particularly for me, he made very good decisions at the breakdown.
"Sometimes in the past… it's one of the things I've spoken about with him. He looked composed and controlled in that environment.
"It's obviously very intense, there's a lot of scrutiny on players in those games, and I thought he dealt with it really well - alongside the other players who were making their early starts in the Six Nations."
With regard to the debate over whose union's player system is better, England's or Ireland's, Lancaster added: "I do think there's ways and means to make it work in England where it can benefit club and country and that was something I always talked about, as you know, and during my time as national coach. But the Irish system works well for province and country."