John O'Shea will not allow friendship to get in the way of precious Euro 2016 qualifying points as he prepares to lock horns with Sunderland team-mate Steven Fletcher.
The pair come up against each other every day on the training pitch at the Academy of Light but will go head-to-head on Saturday with O'Shea wearing the green of the Republic of Ireland and Fletcher in the blue of Scotland, with a trip to France next summer the only focus.
Both men know each other's game inside out but the 34-year-old defender insists they will effectively be strangers for 90 minutes at the Aviva Stadium.
O'Shea said: "Obviously there won't be too much laughing and joking just before the game, but afterwards, it will be the same. You shake hands and you get on with things whatever the result was.
"But look, you know the player, obviously you get on very well with the player, but ultimately, you want to beat him, that's it."
Fletcher heads into the game in confident mood having plundered his first senior international hat-trick against Group D minnows Gibraltar in March.
However, while the Scots pose a serious threat in attack, O'Shea insists it would be dangerous to underestimate them as a team.
He said: "Look, you don't just look at the attacking players, obviously, you look at the whole package and it will be a good test for us, without a doubt.
"They have some good, not just attacking players, they have good players all over the pitch and that's why we know it will be a good test, but one we are looking forward to."
Scotland got the better of the first meeting between the sides in the group when Shaun Maloney's lone strike secured victory in Glasgow in November, and they head into the weekend just a point adrift of leaders Poland, level with World Cup winners Germany and two points better off than Ireland.
Defeat could represent irreparable damage to the Irish cause, but O'Shea is looking no further ahead than the final whistle on Saturday.
He said: "You could easily say that, but there are still games to go in the campaign after this. But we want to win the game tomorrow, and then that will take care of the rest of the campaign, hopefully.
"But we don't look too far ahead. It's a massive game against Scotland, one we are well prepared for and one we are looking forward to."
There has been a quiet confidence surrounding the Scottish camp this week, with Gordon Strachan's men knowing a draw in Dublin would not be the worst result, and the implications of defeat for the Republic.
However, O'Shea and his team-mates are refusing to be distracted by the noise from across the Irish Sea.
He said: "Mind games? Oh my God. Look, we need to win the game if we want to qualify for France.
"No matter who we were playing tomorrow, we need to win the game, so they can say what they want."
Republic of Ireland boss Martin O'Neill will leave record scorer Robbie Keane to decide if he is mentally ready to play in Saturday's Euro 2016 qualifier against Scotland after his family suffered a second tragedy.
PG Wodehouse portrayed only half the picture when he produced his celebrated aphorism about the difference between a ray of sunshine and a Scotsman with a grievance. At times in his career, Gordon Strachan has been the epitome of Wodehouse's grumpy Caledonian.
Maybe Ireland are right to believe that emotional wounds sustained by Aiden McGeady under the command of Gordon Strachan at Celtic Park might just provoke an impassioned and decisive performance at the Aviva Stadium tomorrow.