The on loan Everton winger has flattered to deceive at Hillsborough.
Wednesday fought off a number of suitors to land McGeady on loan from Everton in February, but the Ireland international has struggled to make an impression and was left out of both semi-final ties against Brighton & Hove Albion.
As a result, the 30-year-old, who made the last of his 10 starts as part of a much-changed side which lost to Wolverhampton Wanderers on the season's final day, has been training with his country instead.
"You will have to imagine what that situation might have been.
"Aiden has plenty of confidence, but to not be involved in a play-off final would be disappointing for him.
"For whatever reason between him and the manager, the manager has not picked him, so maybe his confidence will be affected somewhat."
McGeady had this summer's European Championships in mind upon making the temporary switch to Hillsborough, having played just 45 minutes for Everton all season.
But with only one goal and no assists arriving in 13 appearances for Wednesday, the 81-cap international will now have to impress O'Neill in person.
The Republic boss named an initial 35-man squad for the France tournament, and will need to trim that by 11 names by 1 June after Stoke City's Marc Wilson was forced to withdraw.