Sean O’Brien ruled out of Six Nations clash with Scotland at Aviva
IRELAND flanker Sean O'Brien has been ruled out of Saturday's RBS 6 Nations clash with Scotland due to a foot problem.
"Sean has a skin infection on his foot which has failed to recover as quickly as expected," read an Irish Rugby Football Union statement.
Ireland's schedule of four games in four weeks - a product of the weather-enforced postponement of their match against France - is stretching their playing resources.
O'Mahony is highly-rated and is a more natural openside than O'Brien, but the 22-year-old has only won two caps as a replacement against Italy and France in this championship.
The more experienced O'Brien came to the fore last season when his explosive ball-carrying made him a central figure for Ireland and Leinster.
The 25-year-old was switched from blindside to openside flanker during the World Cup and continued to bulldoze a path through opposition defences.
While he has not had the same impact in this Six Nations, he is remains a key component of Ireland's vaunted back row.
They travel to Dublin looking to end a run of five successive defeats and Lamont is looking only for points and not plaudits.
Lamont said: "There is a lot of frustration. That's because we have been playing good rugby, we have just not been getting the right side of the result.
"I think we took the lead three times in the France game and didn't do enough to win the game.
"I think sometimes we play a bit too much rugby in the wrong areas.
"It might be nice to watch but I'd still take an ugly game with a win and a pretty game with a loss. Winning makes it a damn sight easier.
"It's just about the balance and decisions on the pitch at the right time. Sometimes we just need to put pressure back on the team when we have the lead.
"Hopefully we will get the balance right this weekend and it would be ideal to get a win."
Scotland head coach Andy Robinson has devised a plan to deal with Ireland's "choke" tackle but Lamont knows they have to focus on their own game too - and finish the chances that have often gone begging in recent games.
"Ireland are quite unique in their defence," the Scarlets winger said.
"They try to get that hold-up tackle, get the maul formed and get the turnover that way.
"We have been working on trying to combat that. You do change things for every opposition but if we can enforce our game plan and play the way we want to play, with a bit more positional awareness and be a bit more clinical, then I'm sure we will get there."
Scotland secured their only win of the 2010 competition in Dublin, in their last game, and Lamont feels they can upset the odds again.
"It was great to get a win there the last time," he said.
"It's a tough place to go, they have a great fanbase and a passionate crowd.
"We broke a good long run they had at their home ground. We would like a repeat of that.
"Scotland love being the underdogs and hopefully this weekend it will come true for us."
Lamont is back on the wing after Nick De Luca was recalled as centre.
"That's where I play most of my rugby these days but I'm happy to just be involved in the field," he said.
"Jack of all trades, master of none, I can fit in where they want me.
"It suits me, I don't change my playing style too much. I carry hard and try and make my hits, that's basically my game."