This was the third time this season United have thrown away a lead to draw and the second occasion they have surrendered a two-goal advantage to lose two points.
West Bromwich Albion 1 Bolton Wanderers 1: match reportWhatever his motivation, Sir Alex Ferguson gambled by starting with Rooney on the bench after the forward contradicted the manager's claims that he had been absent with an ankle problem.
The issue seemed less relevant when Javier Hernández and Nani gave the hosts a comfortable lead midway through the opening period, but two goals in five minutes after the interval, the first bundled over the line by Patrice Evra and Somen Tchoyi, the second coming from Tchoyi after a bad Edwin van der Sar error, had the crowd baying for Rooney.
The England forward, who has been dogged by accusations about his private life, was thrown on with 18 minutes remaining, playing down the left for the first time since Cristiano Ronaldo's departure.
That cameo brought only one blocked shot and United left the field to boos as it began to sink in that Ferguson's side have drawn five of their eight Premier League games this season. With Liverpool struggling, United have not even faced opposition of much note but 10 points have been dropped in a campaign full of late and bad goals.
'It's inexplicable,' said Ferguson, who lost Ryan Giggs to a recurrence of his hamstring problem. 'The second goal, what can you say? Edwin has been playing for 25 years and the last time he made a mistake like that was probably in primary school so there's nothing you can do about that. It's just one of those inexplicable errors.
'The criticism is we didn't finish them off. We are losing points. It's frustrating. It's not a defining result in terms of where the league is going to end up, but we can't keep doing that. There's two ways of looking at it [being unbeaten in eight matches]. For teams down the league, you say we're undefeated, but for United, it's not good enough.'
Even with Rooney's lack of form, United have rarely struggled for goals this season but, once again, paid dearly for some dreadful defending.
It had all looked so different after 24 minutes. Hernández showed wonderful anticipation
to pounce after Scott Carson fumbled Nani's thumping free-kick and Dimitar Berbatov had missed from close range. Nani later capitalised on a slip from Nicky Shorey to swap passes with Berbatov to double the lead.
Even with United leading, West Bromwich Albion missed a great opportunity when Chris Brunt failed to hit the target from a couple of yards after a Marc-Antoine Fortune cross split the defence.
Nemanja Vidic hit the post with a header from Nani's cross after the restart but then United threw away their advantage yet again.
Brunt drove in a free-kick from a narrow angle that glanced off Evra and bounced off the oblivious Cameroon midfielder Tchoyi and crossed the line before Van der Sar could claw it away.
Shortly after, Van der Sar spilt Brunt's looping cross and Tchoyi touched the ball into an empty net. Half an hour remained but, other than an Evra drive, Carson had little to do.
With Rooney playing in a deeper role, his only opportunity came from an indirect free-kick and, having won 3-2 at Arsenal in their last away match, West Brom,
who lost 6-0 at Chelsea on the opening weekend, were worth their point.
'It was an afternoon of gifts for both sides,' West Brom manager Robeto Di Matteo said. 'We could have gone under. They're full of quality whoever plays. We showed team spirit and the personality that we have in the team and we never give up. That's my philosophy.'