O'Neill believes Aston Villa duo Ashley Young and Stewart Downing are capable of "playing very well indeed" in the right-sided midfield role that is up for grabs in the England squad after Beckham's injury blow.
O'Neill said: "I don't know what the England manager had in mind, whether he was going to take David Beckham or not to the World Cup.
"The news coming out of the England camp suggests that he was - and therefore it is a blow. He has been a very good player for quite some considerable time. On the other hand, as you say, if there is an opportunity there, we have one or two players who actually play and can excel in that position.
"That is down to the England manager."
O'Neill added: "I said last week that, if the likes of Ashley and Gabby (Agbonlahor) and players of that ilk, still have designs left on heading to Africa, every single game they play in will be a chance for them to shine.
"I've heard that James Milner is in a great position to go, one of the reasons being he can play well in a number of positions. When you've got a couple of all-purpose players in your squad, that would suit any manager.
"As for the position wide right, there must be three or four candidates that have got a strong chance. My own view is that Ashley can play there very well indeed.
"Stewart Downing can play there very well indeed. I don't know what the thoughts are (of Capello) but there is still time."