Munster and Ireland will have to do without Donnacha Ryan for most of the season as the second-row undergoes surgery on the toe injury that has kept him out since March next week.
The 30-year-old last played for Ireland in Declan Kidney's final match in charge against Italy in March 2013 and made just 10 appearances for his province last season as he suffered knee and toe injuries.
He joins Ulster pair Dan Tuohy and Iain Henderson in being ruled out of the November internationals - he could also miss the Six Nations.
That leaves Ireland coach Joe Schmidt short of cover behind first-choice locks Devin Toner and Paul O'Connell. Connacht's Mick Kearney trained with the national team on Monday and he is vying for a place in the squad with Leinster's Mike McCarthy and Munster's Dave Foley.
Munster coach Anthony Foley said that the injury is one of the most unusual he has ever encountered.
Foley added that the injury to Ryan is a massive blow to the player himself and also to Munster. The lock-forward is suffering from an unusual toe problem which prevents him from scrummaging but otherwise allows him participate fully in training as he did yesterday.
"It's a weird injury. I haven't come across it before. It is a sesamoid bone - I've become very medical at this stage. It is the bone underneath the toe that you use to spring, so that is why the issue is around scrummaging.
"Yeah, look it is very frustrating. We took an approach with Donnacha to try and get the foot right and he had been doing everything. He was out there training today full-on. He was doing everything, the only thing he cannot do is scrummage and that is the most frustrating part.
"You are looking at him out there opposite us today going at our lineout, going out there full-on and the foot can't withstand any scrummaging.
"So we have done everything in our power but unfortunately it is going to be surgery now for him. It is a bitter pill for us to swallow but we will get on with it.
"It's good opportunities for Dave (Foley), Billy (Holland) and Donncha (O'Callaghan) as well as Sean McCarthy and John Madigan and these lads coming through. We knew this was coming for a few weeks. It is unfortunate but we need to deal with it and I think we have enough in place to deal with it.
"He is still a member of our squad and we will look after him to the best of our ability, and hopefully that means that he is back in four rather than six months, but if it is six months then we will deal with that," said Foley.
Foley is more confident that fellow Irish internationals Keith Earls and Damien Varley will shake off troublesome injuries and be back in action before too long as Munster prepare to take on league leaders Ospreys at Thomond Park on Saturday.
Earls is suffering from a knee problem picked up at international camp in August, while Varley is expected to return in the coming weeks from his own foot problem.
"Keith's is a knee problem. I think he is going to one of the leading consultants on that so hopefully we will get good news. We will be looking at him for next week and having him back in training. He would have trained fully here with us this week, but last week in Cork he took the same knock he took in the knee and he just can't take the pain through it."
Foley said that Argentinian hooker Eusebio Guinazu has linked up with his new team-mates, but will be given another week to settle into the squad, although he trained with them at University of Limerick yesterday.
Foley will be monitoring the progress made by Tyler Bleyendaal after successful surgery to a neck injury and it is now a matter of waiting to see how the New Zealander progresses.
"I got a text from him yesterday saying the operation went well. He is recovering so we are in constant communication with him, the operation has taken place and it was a success so we just need to see how he recovers.
"They have Neil Tucker over there who was the physio here with us, so our physio will be in communication with him finding what the story is," added Foley.