Norway striker Carew found the net for the eighth time in the last seven matches as Villa's striking resources were stretched to breaking point on a night when they needed them most.
He manfully stepped forward to shoulder the burden after Emile Heskey hobbled out of the action early in the first half with an Achilles injury as Sunderland's recent revival continued to gather pace.
Right on cue: John Carew pounces to prod Villa's equaliser past Sunderland goalkeeper Craig Gordon
With Gabriel Agbonlahor sidelined with a foot injury, it was left to Carew to find the net in answer to Fraizer Campbell's sixth goal of the season midway through the first half.
The Villa striker prodded home via the usual source an Ashley Young cross following a delightful move that showed O'Neill's side at its best. Unfortunately for Villa, it was the main highlight on an evening when yet more questions were raised about their top-four credentials.
O'Neill's side remain unbeaten in the Barclays Premier League this year, but this draw was their seventh in their previous 10 outings and their inability to find the killer touch looks increasingly likely to ensure they fall short of their target.
Given Sunderland's soft underbelly away from Wearside, this was a game in which the onus fell heavily on the hosts. But O'Neill's pre-match assessment that Sunderland had been 'rejuvenated' recently proved uncannily accurate.
First up: Fraizer Campbell celebrates his opening goal with team-mate Darren Bent at Villa Park
He said: 'Naturally, we are disappointed but Manchester City's result keeps us there. Tottenham will be delighted, they are the main beneficiaries, although they have some tough fixtures.
'But if you made the point that draws could cost us, I couldn't disagree. If we had been able to score in two of those games, it would have made a massive difference.
'What continues to give me heart is that we are capable of going away from home and winning. But this was two points dropped.'
What is of greater concern to Villa's boss is the injuries he is suddenly picking up. Richard Dunne, James Milner, Agbonlahor and Heskey are all doubts ahead of Saturday's trip to Chelsea.
As for Bruce, he orchestrated another frustrating evening for Villa's fans. He has been beaten just once at Villa Park in six visits as a manager with Wigan Athletic and Birmingham City, although he had cause once more to be grateful to keeper Craig Gordon.
Two saves inside the first 10 minutes laid the platform for this point. Two quite magnificent reflex stops from Carew and defender James Collins were followed by another to deny the Norwegian in the second half as Villa ran out of ideas.
Pain game: Emile Heskey leaves Villa Park a dejected man after being forced off early with an injury, prompting fears over his World Cup future
But Sunderland, with Darren Bent looking a pedigree forward, carried a threat. It was their leading scorer who came short, allowing Campbell to run in behind Villa's backline. Kieran Richardson's sublime pass split the home rearguard and the £5m striker lifted the ball over Brad Friedel.
MATCH FACTS ASTON VILLA (4-4-2): Friedel 6; Cuellar 6, Collins 6, Dunne 6, Warnock 6; downing 6, Milner 7, Petrov 7, A Young 7; Carew 8, Heskey 5 (Delfouneso 14, 6).
SUNDERLAND (4-5-1): Gordon 8; Hutton 7, Turner 7, Mensah 7, (Da Silva 71, 6) Ferdinand 6; Campbell 7, Cattermole 6, Richardson 7, Henderson 7, Malbranque 7 (Cana 81); Bent 7.
Man of the match: John Carew.
Referee: Mike Dean.
'We have played a lot better with a settled side,' said Bruce. 'We have got a few more of our big players back and it's made a big difference. That's one out of nine we have lost and that was to Arsenal. We are more resilient.'
He did concede that Gordon had played a major part once more.
'The keeper has been terrific,' he added. 'He is a case in point, actually. He broke his arm at Spurs, had a plate inserted in it and was out for three months. But he's come back and is looking the part.'
Bruce is now hoping that one more victory should ensure the minimum target for the season safety is met. He left, though, with a message of encouragement for the hosts.
'Villa have been absolutely excellent this season,' he said. 'They have had a magnificent season, reached the Carling Cup final and they are in the semifinals of the FA Cup. They are also having a crack at the top four.
'What more do the fans want?'
O'Neill could certainly answer that.
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