"It's terrible news because he played every single game last season. He was fantastic, but he'll come through it."
Barry received a warm reception from the home fans when he came on to replace Bouma.
The England midfielder has openly stated he wants to join Liverpool and he was booed by the Villa support in a friendly on Wednesday.
O'Neill says he is still waiting for an improved offer from the Reds and remains hopeful the 27-year-old will stay put.
"Having not heard anything from Liverpool for some time it is clear we value him more than they do," said O'Neill.
"We obviously don't want him to go, so the price we are asking is a fair and realistic one for a player who is so good. In fact I think it is really cheap.
"My own view is that he should hang around for another year and see if we can make further progress as he would want.
"Gareth is still only 28 next year - if we don't get where he wants to go, everybody would wish him well."
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