Proud though he is of having helped turn a team expected by many to be once again battling relegation into genuine promotion-contenders, the Irishman can't quite escape the feeling of injustice as he reflects on Saturday's 3-2 reverse in the East Riding.
Having twice fought back from a goal down through second-half strikes from Marcus Day and Fatlum Ibrahimi, the Rail were eventually undone by Niall Tilsley's 84th-minute header - a goal O'Connell is adamant should not have stood.
And that was not the only refereeing decision that he insists cost the Starbeck outfit on the day.
"I feel aggrieved. I feel robbed. North Ferriby haven't beaten us in that game, we've been beaten by the officials," O'Connell told the Harrogate Advertiser.
"There are three big decisions that have all gone against us on Saturday. You can accept one because referees are only human, they make mistakes, maybe even two, but all three of them? It's completely unacceptable in my opinion
"It's really hard to take. It would be in any game, but in a fixture of that magnitude, you can't have the officials getting three big decisions wrong like that in a play-off final.
"These moments change games, and not one of them has gone for us. Not that it counts for anything because we've lost the match, but I thought that we were the better team on the day, I thought we controlled big periods, so we didn't deserve this.
"In fairness, if you look at things over the course of the season, North Ferriby deserve to be promoted. They finished second with 96 points, which is 13 more than us. So, fair play to them for that. But Saturday was a one-off game and I don't feel we should have come away losing."
The decisions that O'Connell has been left so angered by all came after Railway had composed themselves having made almost the worst possible start to proceedings in falling behind to Oli Donald's second-minute opener.
"At 1-0 down just before half-time, Dan McDaid swings an unbelievable corner in and it beats everyone. That should have been 1-1," he added.
"It's a routine we've worked on a lot. We've used it plenty of times this season and it's brought us a lot of success. I asked the referee at half-time why he disallowed it and he said the goalkeeper has to be allowed to come for the ball and someone was obstructing his view.
"There was one of our players in front of him, that's his job. I asked him if there was a foul on the keeper, was there even any contact made with their keeper? He said 'no' to both questions. It just doesn't make any sense. You can't disallow it, 100 per cent.
"Then, at 1-1, Marcus Day gets the wrong side of their centre-half (Tilsley) and there's a blatant handball. The lad came up to me after the game and apologised. He said it was just an instinctive reaction. The linesman saw it and gave it but the referee said 'no'.
"Late on their lad (Tilsley) has jumped on top of Mike Morris and taken both him and then Elliot Holmes in the back of our net as he heads in their winner. It's a foul and it's one you certainly have to give if you've disallowed our 'goal' when there wasn't even any contact on their goalkeeper."
In terms of his players' performance against a side who beat them 6-0 when they travelled to Ferriby during the regular season, O Connell doesn't feel they could have done any more.
"Ferriby are a very strong team. They've thrown a lot of money at trying to get promotion and, as I said before the game, there are no real weaknesses in their line-up," he continued.
"So, to come here and go toe-to-toe with them, dominate possession for periods of the game, have more entries into the final third than them and probably more shots on target, it's a superb effort.
"I don't think they've tested our goalkeeper in open-play. They relied on set-pieces. Their goals came from a corner and two long throw-ins, which is a great weapon for them and we found it really hard to defend.
"They battered us when we came here earlier in the season, so I think the fact that they showed us so much respect and sat off us for long periods says a lot.
"I think this performance shows how far we've come this season and how good a team we are."