'At this stage you expect Jack to star in every game' - Victor Costello believes it's Conan's time to shine
Conan backed to make a major impact for province and country in career-defining year
All the way up through the ranks Jack Conan was the most important player on his team. At 26, he is assuming that mantle for Leinster.
Increasingly, it is the No 8 who emerges when the chips are down and the European champions need someone to step forward and make a game-changing play.
When his team was struggling against Ulster, minutes after Jacob Stockdale's failure to land his grounding, it was Conan who stepped forth and wrested momentum back.
There didn't seem to be much on when Seán O'Brien went to ground on the opposition 10m line and Rhys Ruddock cleared the ruck, but the No 8 made something happen.
He barely broke stride as he whipped the ball from Luke McGrath's grasp and stepped through Eric O'Sullivan's tackle before accelerating beyond Rob Herring's grasp. Even his falling shorts couldn't stop his momentum as he sized up Michael Lowry before brushing him off and, when Stockdale made it back and went high to try and stop the offload, Conan rode the challenge and off-loaded to Adam Byrne to score.
It was a moment of real quality when his team needed it, but it was only part of a high-octane, 80-minute display from a player who has hit peak form at just the right time.
Against Ulster, he carried 16 times for 67m and beat six defenders. Without the ball he made 16 tackles and missed none.
"He just seems to be playing with so much confidence at the moment," scrum-half McGrath said of his No 8.
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"Maybe that was from when he came on against France and was brilliant. He's really moved on from there.
"Everybody loves playing with him, he's so skilful as well as being a big strong ball carrier, so he's very enjoyable to play with and we need a big game out of him this weekend."
Sunday's opponents will know all about Conan's threats; when the January game between Leinster and Toulouse was still poised at 3-3 before half-time, it was Conan who carried at pace to score a crucial try.
His tendency to deliver at key times is well known, but on his one Six Nations start for Ireland this season he hit 37 attacking rucks and made 17 tackles in an impressively hard-working display.
At 26, Conan might have expected to have more than 14 caps but, having succeeded Jamie Heaslip at Leinster, he's found himself behind CJ Stander in the Ireland pecking order.
In the past, he has spoken about the feedback he's received from Joe Schmidt about being present for every moment of the game.
"He was a great ball carrier when he initially started as back-up for Jamie when his career was coming towards the end," Victor Costello said of his successor in the Leinster and Ireland No 8 shirt.
"Leinster picked him and he used to kind of go missing in the big games, like Clermont away (in 2017) when they made a massive comeback and when things were going well he was there carrying and was very prominent, but when things weren't going well, like other players, he wasn't.
"But now it's kind of like the second coming of Jack Conan, he is doing all of the hard work but also taking opportunities.
"If you look at that try he set up against Ulster, he made the break, had the confidence in the offload and the composure. That is a true international.
"You look at Drico (Brian O'Driscoll), Jamie (Heaslip) and these guys who burst on the scene and maintained a really high level... Jack is learning. In terms of his all-round play he is really very much the finished article and improving.
"He'll be in people's faces and minds as a super, world-class player. He took a while to get there, but he got there."
On Sunday, there will be a number of Leinster players searching for form as they take to the pitch.
Johnny Sexton hasn't played for the province in 2019, Seán O'Brien is out of form while Robbie Henshaw and Devin Toner are just back from injury and a couple of others have not yet hit the heights of last season when they beat all-comers en route to the final.
Conan has become a rock of consistency amid the form-dip and his form could put him front and centre of Schmidt's World Cup plans.
With Dan Leavy out of the tournament, Josh van der Flier in a race to be fit and O'Brien still searching for form, the coach could look to a re-jigged formula with Conan joining Munster pair CJ Stander and Peter O'Mahony in the same back-row that started the final Test in Australia last June.
While Stander adds so much to the team, he is slightly blunt in his approach. Costello believes there's a case to be made for Conan.
"There is a lot of competition, but he is now becoming a spearhead at No 8 and crucial to the all-ground game - when you're defending, when sleeves are rolled up and also the big moments of the game, he's there," he said.
"I know CJ Stander's form came back a bit during the Six Nations, but compared to Jack Conan he is becoming a bit one-dimensional.
"Definitely, Conan is the form No 8 and at this stage you expect him to star in every game for Leinster and Ireland. His work-rate is huge. There's all this talk about the unseen work people do. His unseen work is visible, if that makes sense.
"Conan's physicality at the breakdown, his commitment to the set-piece where he's a lineout option as well is very visible and that's what gives him the opportunity to make those breaks.
"Now he's making those breaks while doing the hard work and hard yards in defence and attack.
"That's what makes him the player he is now."
That player will have a big say in Sunday's semi-final and, it appears likely, many more big days in 2019.