Curtis Davies, Nigel Reo-Coker, Nicky Shorey, Steve Sidwell, Luke Young and Habib Beye were informed this week that the club are ready to listen to offers for them, with the Villa boss needing to sell to raise most of his transfer funds for this summer.
All six found themselves on the periphery last season with O'Neill largely opting to stick with the same side.
The Villa manager admitted he could understand why the players would be disgruntled, but maintains they must look at their own performances before pointing the finger at him.
"We will look at things," he told the Express and Star. "Of course, there will be players here whose future, in terms of playing regularly in the side, might lie elsewhere. I think that's natural.
"Players, despite maybe a number of reassurances from a manager, will view the number of times they've played this season and say 'listen, I could go and play elsewhere'.
"In terms of the slate being wiped clean, players don't always see it.
"It's up to them to think: 'I've got the ability, I've got the determination to do it and I'm going to get through and break into the team. If I've done my utmost and the manager still doesn't pick me then I can consider myself really unlucky'.
"And on occasions that does happen, definitely.
"But during the course of the season I don't think you can always point to a spate of bad luck, particularly if you've been fit."
Meanwhile, Paul Faulkner has been appointed Villa's chief executive with immediate effect.
He was previously the club's chief operating officer.
He said: "It is a real honour and privilege to have been involved with this great club since Mr Lerner's takeover in 2006 and I look forward to continuing to work alongside the fantastic people we have at Villa Park and Bodymoor Heath as we now start to prepare for the 2010-11 season and beyond."