'Ashley Young is on a par with Lionel Messi'
Asked if Young deserves to be described in the same company as the Barcelona playmaker, and Manchester United's Cristiano Ronaldo, O'Neill replied: "Yes. In my opinion. I see a lot of games in Europe, I watch a lot of football, and you see a lot of players in the game who are very functional.
"Some are decent, some are more than decent and some are very, very good. And then you have the players who are absolutely exceptional. And Ashley Young is absolutely exceptional."
Describing the second of the 23-year-old's two goals against Everton at the weekend, O'Neill added: "Could you name me two dozen players in the world that could have scored that goal? I really can't.
"To have the presence of mind when Gabby [Agbonlahor] placed it through, to size up the situation in that time, to go immediately to attack the centre-half, and then to whip it round [the goalkeeper], all in the last minute of a game which he has worked tirelessly through the course of the match - just to have the energy to do it was remarkable.
"But to have that poise was world class. I think he is a world class performer, and I don't use that word too often." Young's rise in recent weeks has come as a surprise to many who previously assumed that the most interesting thing about the player was the fact he used to go to school with Lewis Hamilton.
O'Neill, who spotted the winger's potential and bought him from Watford for £8m last year, agrees that the winger has exceeded even his expectations. However, he suggests that there is yet more to come.
"I think the speed of his improvement has surprised a lot of people," he said. "He has developed enormously in the two seasons. I think he has surpassed expectations. He has far from reached his peak. If you look at other top quality players, players aged 22 to 23, who are absolutely brilliant - people like Messi and Ronaldo - you ask 'how can they improve?' They just do. They just get better. They see the game differently than they might have done three years earlier."