McGrath's fitness the key to solving Leinster puzzle
There are bigger names with more caps in the vast Leinster squad, but increasingly Luke McGrath is the most important name on Leo Cullen's roster.
The obscure law that forces the province to pick two of their three Antipodean 'non-European' signings Jamison Gibson-Park, Scott Fardy and James Lowe each week limits the coach's options and if McGrath is not fit, forces his hand.
In the biggest games such as the Champions Cup quarter-final against Saracens, the coach has gone for Lowe and Fardy, with Gibson-Park missing out and Nick McCarthy covering McGrath on the bench.
McGrath picked up an ankle injury in that game and the inexperienced McCarthy struggled when introduced on the biggest stage of his career to date.
The 23-year-old has been a regular on the Leinster bench, but has only been entrusted with two starts this season.
If McGrath isn't available for the Champions Cup semi-final against Scarlets, Gibson-Park will start and that means Lowe will likely miss out given Fardy's importance up front.
The mood around the Ireland international is positive. His ankle is no longer in a protective boot and while he won't feature against Benetton this week, Leinster hope he will be fit for the Aviva Stadium clash.
Assistant coach Girvan Dempsey conceded that the rule adds to the importance of having him on deck.
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"Definitely, that adds to it. That's why we are making sure we don't throw him in this weekend, get him ready for the games coming up," he said.
"Luke's been excellent, (he) has had a superb season. You look at him and see how he has progressed his game, what I remember seeing in him as a young kid in St Michael's is that he just had an abundance of energy and he was like a ball of energy, involved in everything.
"It was about trying to curb him in his understanding of his role as a No 9, that he was nearly playing as a No 7 because he was in nearly every breakdown. He was getting poaches.
"It was tough because it was impacting on how the back-three worked and how his defence happened. He was stuck in the breakdown and we wanted him to play quick.
"It was an education for him as a young kid coming out of school to where he is now. You have seen that this year in particular. I think his kicking game has really improved. His passing game has improved, definitely. It's just his sharpness, that real zip with his strength when he is on the ball and the speed at which he can clear allows us to play quick.
"He's growing and maturing nicely in terms of big games, exposure in those big games. That's what he's learning a huge amount from.
"You can see he's got the right temperament, he's shown that through captaincy through schools, age-grade right up to us at senior level. He's one of the leaders that we look to as well."
Dempsey is happy with Leinster's depth at scrum-half.
"You look at all of our No 9s, you look at Nick and Jamison and Charlie Rock, they've all been excellent this year," he said.
"Nick has progressed really well, he's another one similar to Luke out of St Michael's, came through age-grade and was an excellent player through age-grade.
"His passing game has been really, really solid and sound over the past few years. What he's added this year is that experience of playing in big games.
"Jamison, his ability to see and play a different type of game for us as well. His long passes, some of his passes from a 20m ruck to the edge to put James Lowe away or something like that, (add) a different dimension.
"They all have different strings to their bow, they play different ways. It's a great headache to have to have that in terms of some quality No 9s around, because we've needed them."
McGrath is just one of the concerns on Cullen's radar ahead of the season-defining Scarlets clash. Rhys Ruddock and Jack Conan won't face the Italians and are also doubts for the semi-final.
Dempsey is "hopeful" that Seán O'Brien will play this Saturday, while Jordan Larmour, Noel Reid, Ed Byrne, Tom Daly and Michael Bent are fit again.
"He has made progress," he said of O'Brien.
"We are very, very hopeful he is going to be involved this weekend.
"He knows he needs more minutes under his legs, more game time. He has made huge progress. We're very confident he's moving in the right direction."