It is unlikely to be hate mail, even from the 300 fans who forked out good money and braved sub-zero Russian temperatures to see a reserve side beaten 2-0 on the night, 3-1 on aggregate.
The consensus amongst those die-hards is while disappointed with O'Neill's controversial selection policy, they can hardly chastise a man who has done so much for their club during his two-and-a-half -year reign.
O'Neill appreciates, though, there will be a number who will not see it that way, and so he is bracing himself for the backlash.
"We had a travelling group of people who spent a lot of money to come and support us, and of course they'll be disappointed," said O'Neill.
"We will try, at some stage or other, to make it up to those people who made that journey across. There are a lot of people who are Aston Villa fans who were unable to afford the trip still supporting us. I am hoping that.
"I know, though, I will get plenty of letters from people saying it was the wrong thing to do, and I have to cope with that. But if you're going to ask me is Champions League football the immediate result of my decision, then I'm sorry, no. I can beat myself up enough without other people beating me up.
"But it's where I want the football club to go, and at this minute we're making strides towards that. However, whether we make it into the Champions League this year or not is not the point. Would I have looked at our position if, for instance, we were in the quarter-final? I may well have done so, but we weren't. It was the final 32.
"So we're going to try and progress, and the point is, if we're in this position this time next year, that we are able to cope. Manchester United, Chelsea, Liverpool and Arsenal, and you can imagine Manchester City and Tottenham, being able to cope.
"That's the competition, and that's where we are, and after these experiences, European football is something I want to continue to remain involved in."