Ireland dealt World Cup blow as veteran flanker Sean O'Brien is ruled out of tournament with hip injury Leinster flanker Sean O'Brien is one of Ireland's most experienced players He is out for six months and will have to undergo surgery on hip injury Joe Schmidt is already without Dan Leavy for World Cup in Japan this year He will lean heavily on Josh van der Flier and Jordi Murphy to carry load By Rory Keane for MailOnline Published: 23:38 BST, 26 May 2019 | Updated: 23:38 BST, 26 May 2019 Viewcomments Joe Schmidt has suffered a World Cup injury blow with veteran flanker Seán O'Brien ruled out of the tournament in Japan with a hip injury. Ireland's head coach is set to name a 45-man preliminary training squad early this week, and the Kiwi will have to prepare for the global showpiece in Japan without one of his most trusted and experienced forwards. Schmidt was already without the services of Dan Leavy - who is recovering from a complex knee injury - meaning he will lean heavily on Josh van der Flier and Jordi Murphy at the World Cup. Sean O'Brien (ball carrier) will be a huge loss for Ireland in Japan at the World Cup O'Brien will undergo surgery in the coming weeks and is facing six months out of action. The 32-year-old has signed a three-year deal with London Irish, effectively ruling him out of further international recognition due to the IRFU's stance on selecting overseas-based players. 'Everyone at Leinster wishes Seán the very best of luck with his recovery and with his move to London Irish later in the year,' read a statement from Leinster on Sunday. The news on O'Brien tempered an otherwise positive weekend for the province who claimed back-to-back Pro14 titles with a hard-fought win over Glasgow in the Grand Final at Celtic Park. Fittingly, O'Brien - after 12 seasons of service - was given the honour of lifting the trophy. 'I think he's a fantastic leader, a fantastic player, a fantastic character and a fantastic personality,' said Stuart Lancaster, Leinster's senior coach. 'I think he'll be massively, massively missed by Leinster. I think I didn't really get the benefit of really coaching him the way in which I wanted because the three years in which I've been here, he's been injured for quite a lot of that period of time. The powerful flanker will join London Irish next season but is set to be out for six months 'But his qualities still shone through and I thought it was a great testament to the team, and to Johnny in particular, that he would give Seán the opportunity to raise the trophy because it's been an emotional few weeks for Seán to leave Leinster, and we all feel his disappointment that he has to leave.' Meanwhile, Johnny Sexton is already gearing up for Ireland's World Cup tilt in Japan. This is set to be his third World Cup after featuring in the 2011 and 2015 editions, and the 33-year-old is targeting a big campaign in September. 'Japan has been at the back of everyone's minds for ages, it's very hard not to think about it,' he said. 'We'll enjoy this tonight and tomorrow, we've our ten-year (Heineken Cup) reunion on Tuesday and Wednesday so I'm looking forward to that to seeing some old faces again. But, no, I'll take a rest and try and stay in as good shape as possible to come back into pre-season which is going to be a big five, six months for the whole country really.' Johnny Sexton, fresh from winning the Pro 14 title, is already thinking about the World Cup Share or comment on this article: All rights reserved for this news site dailymail and under his responsibility