By SABC Sport
4th October 2023
Andy Farrell's men will top Pool B and qualify for the quarter-finals by avoiding defeat in Saturday evening's crucial Paris clash with Scotland.
Ireland could even progress to the last eight with a loss but that would be dependent on the Scots margin of victory and bonus points gained.
Sheehan is eager to avoid "over-hyping" a pivotal Stade de France showdown which will also determine the fate of reigning champions South Africa.
While the 25-year-old hopes to emphatically banish any prospect of elimination by helping his country register a 17th consecutive success, he insists Ireland's squad are au fait with all possible scenarios.
"We're all aware of the different little permutations, but our job is to go out and win a game," said Sheehan.
"I'm sure there'll be scenarios throughout that, if we find ourselves in a situation, we'll know what to do, and it would be stupid of us not to know it going into a match.
"Of course everyone is fully aware of what we need to do at what time and depending on what the scoreline is."
South Africa top arguably the competition's toughest pool with 15 points from their four games, with Ireland and Scotland on 14 and 10 respectively ahead of what could be a tense encounter in the French capital.
Tournament regulations state teams level on the same number of points at the end of the group stage will be separated by their head-to-head result in the first instance.
However, in the event of a three-way tie, the nation with the best overall points difference will top the pool, with head-to-head then used to rank the other two.
"Obviously there is a lot on the line, especially this week," said Sheehan.
"But I think we probably stick to the same procedures in regards to preparation. I think you can be in danger of over-hyping a game or getting too feared up about an occasion, so realistically it's pretty similar to a Test match, but obviously everyone knows that there is a lot on the line."
The weight of expectation is firmly on in-form Ireland, with comments from Springboks director of rugby Rassie Erasmus and head coach Jacques Nienaber ramping up the pressure.
Sheehan is uninterested in the outside noise and pays no attention to press coverage.
"I don't read or contribute to any sports media really," he told reporters.
"I was just like that as a kid, I wasn't really interested in¦ in your job, really. It's just another Test week for me and I sort of focus very much on what's going on in the camp and what people tell me within the camp."
Leinster man Sheehan is pushing for a full World Cup debut this weekend.
He returned from a foot injury as a replacement in Ireland's 13-8 win over South Africa on September 23 following a layoff which also allowed him to rehabilitate shoulder and hip niggles.
"I feel in a great place, probably the fittest and the best condition I have been in a long time," said Sheehan.
"It was nice to have that rehab window, where you can focus on other things as well. The body is in great shape."