There are concerns from some quarters that the Premier League is on the slide.
But O'Neill says: "I don't think you can read an awful lot into the Premier League not having a representative in the last four.
"In one particular season, if Liverpool had not been paired with Chelsea in a quarter-final, you could have had all four representatives in the semi-final. Does that mean La Liga was weaker because of that? I don't think so.
"Barcelona at this moment are the best team in European football and possibly the best team in the world and they play in a league with Real Madrid.
"But that does not mean that you can be smug about your own particular league."