The Austrian striker, 21, made his Aston Villa debut in 2010 â€“ a year after Clark played his first game for the Villans.
And the pair have become close pals at Villa Park â€“ but their friendship will be put on hold when they face each other for their national teams when the two countries meet at the Aviva Stadium.
The Ireland defender said: â€œAndi and I have had a chat about the game and I reckon we have a good enough squad to get a result against them.
â€œHe is one of my good mates, one of the lads who has been at the club since he was 16.
â€œSo we get on really well but if weâ€™re both playing on the day there wonâ€™t be any love lost."