Harewood became O'Neill's second summer signing at £4million from West Ham but did not score in five pre-season outings and stayed on the bench during Villa's opening day defeat to Liverpool and their weekend draw at Newcastle.
"And Marlon is certainly capable. It is no concern to me. It is not a bad signing at all.
"You can't always get the best apples out of the tree all the time. He is fairly typical of the modern player, it is just the all-round consistency that separates the top-of-the-tree players from those who eek out a living.
"The season before last he was marvellous and people were eating their words. Then last season everything that could go wrong, did go wrong for West Ham. So it was no surprise that the team was broken up, but I think he can do well from this."
Harewood scored just four goals last season, but Little is convinced there is no lack of self-belief.
"I'm not sure if it is a confidence thing with Marlon. Ipswich stormed the top division then fell away, the same with Wigan last year.
"It is quite difficult to maintain that level of progress," he said. "The better players get courted by the bigger clubs and if you hang on to them then you can lose spirit within the club."