Villa slipped into the relegation zone with defeat, with pressure increasing on boss Gerard Houllier.
He told: 'Everyone is devastated. We were definitely the better team in the first half. I don't think they caused us problems or created any chances. We had a couple of chances in that first half and maybe if they'd have gone in, it would have been a different game.
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'Obviously before Emile's (Heskey) sending off we were on top. But it's just one of those things that happens.
'There was the sending off and then we had to dig in and push for the late goal. It just never seemed to come.
'The lads were all just gutted in the dressing room. After the high of Chelsea, to come back to Villa Park and lose to Sunderland was absolutely devastating.
Clark insisted Villa now need to pick up their form.
He added: 'Like the gaffer said, we need to pick ourselves up and go again now.
'I am confident we can turn it around - and all the lads share that confidence too.'
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