"The exertions of international matches, players travelling all over the place, does take its toll, but all the clubs are in a similar position," the Villa manager said. "Manchester United also have players travelling everywhere and have had similar experiences to ourselves.
"We might start to change things around a little bit now. I just felt that some of the international players looked a little bit leggy. Gareth looked drained and not the usual Gareth Barry we've come to know and enjoy."
O'Neill used last week's international break to send Nigel Reo-Coker away for a short holiday and may do the same with Barry after Christmas.
"Nigel Reo-Coker had no break in the summer after captaining England Under-21s in their [European Championship] tournament and then coming straight into the transfer to us, so he's had a week's break. So I hope at some point during the course of the season, maybe if England do qualify and they're through, we are able to give somebody a break for a few days. But Gareth Barry loves his football and he wouldn't want to [have missed] a game like Man United.
"That's for the future. Ashley [Young]'s gone away with the England squad, had a great experience, better than a week's rest even if he didn't play. It's great for him and for Scott Carson."