Luke McGrath's knee ligament damage sustained during Leinster's victory over Toulouse will keep him sidelined for eight weeks and therefore largely rule him out of Ireland's Six Nations Championship campaign.
Injuries are rarely opportune but the timing of the 25-year-old McGrath's misfortune is particularly cruel, especially given his excellent form. Connacht's Kieran Marmion, scheduled to return soon following surgery, and John Cooney (Ulster), who pulled out of his province's win over Racing 92 last weekend, are likely to be the main beneficiaries as they battle to understudy Conor Murray.
Leinster too must move forward without McGrath and another injured scrumhalf in Nick McCarthy, starting in Sunday's final Champions Cup pool match against Wasps in Coventry.
Jamison Gibson-Park will start, former Ireland Under-20 international Hugh O'Sullivan (20) is expected to be on the bench, while academy prospect and UCD student Patrick Patterson (20) was registered by Leinster on Tuesday, making him eligible to play in the European tournament.
Leinster scrum coach John Fogarty has been impressed with the maturity of attitude and performance that O'Sullivan has shown in a fledgling professional career that numbers just six appearances for the senior team. "With Hugh, he's a very different character than I'm used to.
“His mindset is very impressive. His composure, his confidence, natural confidence not cockiness, he has in his [qualities] and what he can future-add is impressive. He’s not as fazed if you put him into a situation as other guys [are]. You test the water in training sessions, A games and Pro14 games and he’s quite composed in pressure situations.
"Another person would be Scott Penny, thrown in, in his first game, he just continued to be himself and that's something Hugh does really well. He doesn't try to be this, that and the other. He doesn't try too hard in other areas, he's very composed and confident; he's been able to mentally step [up].
“That’s not an easy thing to do for a young player to be able to come in, to be able to deal with Sexto [Jonathan Sexton] or Ross [Byrne] as they demand such a high standard. That’s different to other guys; that’s not a typical thing.”
Gibson-Park (26) works in closer proximity to O’Sullivan, part of the scrumhalves’ club and was complimentary about the player who will understudy him on Sunday. “Ah Hugh is a hard-working little bugger. There’s no doubt he’s been in the building . . . sorry, he’s always in the building.
“He’s supposed to be [going] home but he’s always in the gym doing other stuff so yeah, he’s hard working and he’s picking a lot of brains seeing where he can get better. He’s worked hard on his kicking since he got in and I’ve seen massive improvements in that. Yeah, I’ve no doubt if he’s called upon he’ll be ready to go.
“Hughie has figured in a good few match-day 23s already. Patsy [Patrick Patterson] has only played the one game, off the bench against the Dragons. He’ll be looking forward to getting a few more minutes and showing what he can do.”
Gibson-Park has endured the frustration of not alone battling rivals for the nine jersey but because of the foreigner rule – Leinster coach Leo Cullen will have to decide whether James Lowe or Scott Fardy sit out Sunday's game – contesting those two available places with world-class players.
“I obviously have two other guys to compete with who are out of my position. That makes things a little more difficult at times especially when you are missing out through something that is un-rugby related; it can be frustrating. That’s all part of it but we are nearly at the end of it which will be nice. I still have a few more months of it to go,” he said.
It’s a reference to the fact that he will qualify to represent Ireland in June something that will simplify the foreign player conundrum. He’s won over 50 per cent of his Leinster caps off the bench but this season has made eight starts in 13 appearances, albeit none of those run-on roles have been in European competition, a statistic that will change come the weekend.
"Yeah it can be frustrating. There are times when you want to be starting the big games. At the same time you have a part to play; there are 23 people in the team not 15. A lot of games are won off the bench. There is that kind of opportunity." This is something he proved with his quick thinking in ensuring Leinster's bonus-point try for Adam Byrne against Toulouse.
He’s played with the two best outhalves in world rugby, Beauden Barrett at the Hurricanes and Sexton at Leinster, so how does he rate Ross Byrne? “Rossy’s improved out of sight since I got here. We’ve played a good bit of footy together and I’ve just slowly seen improvements.
“Obviously playing and training alongside Johnny has a lot to do with it. I’m looking forward to linking up with Rossy a little bit more over the next while. He’s obviously got a different temperament to Johnny,” he smiled.
“He’s [Byrne] the master of the kick pass as we’ve seen; his kicking game is pretty awesome. Just all over the park, he’s improved out of sight. It’s awesome to see him apply that little bit of pressure on Johnny as well. It’s good for us.”