O'Neill confessed: "I don't know how the fans will react - and whatever I say won't make a jot of a difference.
"But is that what England fans, still despondent from not qualifying, really want to hear?"
Carson is guaranteed to start for Villa against Boro at the Riverside today.
O'Neill plans to have talks with the keeper and Villa skipper Gareth Barry, who also figured in Wednesday's Wembley defeat.
And the Irishman insisted: "Scott will be disappointed. But he's 22, which is incredibly young for a goalkeeper. He has plenty of time.
"Peter Shilton made a mistake in 1973 against Poland and only turned out to be the best keeper in the world.
"Our goalkeeping coach Seamus McDonagh spoke to Scott on Wednesday night - and I will be talking to him, too.
"He will be down. But I am sure that Scott is strong enough and will want to play the game.
"He did well in his last Villa match against Birmingham and that's how I should judge it."