But this evening's encounter will draw comparisons with last year's match between the teams at the same stage of the competition, when the Foxes won 2-1 after being 1-0 down with two minutes left.
Leicester went on to reach Wembley, losing to Tottenham in the final, but O'Leary refuses to harbour a grudge over that setback, which came less than a month after he took over as manager at Elland Road.
"We've nothing to avenge because we've already gone back to Leicester and won since then," he said. "Conceding the two late goals that beat us at Leicester in the cup was one of the lows of last season. We had dominated the game and we were in the lead with only a couple of minutes left."
Meanwhile, O'Leary is dreading the prospect of putting his young side through another two hours of football. Tiring trips to Moscow (twice) and Sofia, together with a regular diet of domestic matches every weekend, have taken their toll on the Premiership leaders.
O'Leary remarked that his team were weary after Sunday's defeat of Port Vale in the FA Cup and a visit to face Martin O'Neill's hard-working side is arguably the last thing he would have wanted to subject his players to. But the stakes are high, with a quarter-final tie at home to Fulham awaiting the victors.
Leeds could again be without David Batty as he struggles to recover from an calf injury.
Meanwhile, O'Neill has refuted suggestions that Emile Heskey is about to leave Filbert Street, insisting that the player has not signed a pre- contractual arrangement with Liverpool.
Recently renewed speculation has linked the highly rated England striker with a pounds 7m move to Merseyside, but O'Neill yesterday moved swiftly to deny the suggestion.
"There is no agreement with Liverpool," he said. "I know Emile has his preferences but there is no written agreement.
"I thought he was going to leave last May. I don't expect Emile to spend the next 15 years at Leicester, however much I would like him to, and when he does decide to go, he will not be short of offers."
Leeds themselves are one of several clubs to have been linked with Heskey in the past, and will have noted O'Neill's comments with interest.