Lampard and his team-mates were left fuming after being denied a 'blatant' penalty in the 1-0 defeat to United, which left their season on the brink of unravelling completely.
Patrice Evra appeared to chop down Ramires in the dying seconds at Stamford Bridge, but Spanish referee Alberto Undiano Mallenco became the latest official to rule controversially against Chelsea in a crunch Champions League match in recent seasons.
Floored: Ramires (right) felt he was fouled by Evra (centre) inside the area
Midfielder Lampard, who will not have happy memories of what was his 500th appearance for the club, does not want his team-mates to feel sorry for themselves in the build-up to Tuesday's second leg at Old Trafford.
'We can't really think like that too much because it's negative thoughts,' he said. 'We just use it to motivate us, really.'
'Everyone knows it was a penalty, but he didn't give it - simple as that. I can't believe he didn't give it. It was blatant - everyone in the stadium saw that.'
Mallenco is the same referee who disallowed Chelsea a Champions League goal at Juventus two years ago, despite the ball being a whole foot over the line.
Lampard added: 'Things do sometimes go in your favour and sometimes they don't.
'It seems in the Champions League that we've had some bad luck.'
As well as the penalty incident, Lampard was desperately unfortunate not to equalise when Evra cleared his shot off the line, but otherwise Chelsea found chances hard to come by.
'We didn't play as well as we can do,' Lampard said. That's probably what I'd look at mainly rather than the decision.
Small margins: Lampard (left) watches as Evra (right) clears his shot off the line
'You wanted to keep a clean sheet and you wanted to try to win the game at home, so it's not the result we look for.
'But it's half-time and we have to remain confident that we can go and win, as we've done before at Old Trafford.'
Chelsea have a better record there than almost anyone, clinching a 2-1 victory in what proved a Barclays Premier League title decider last season.
'We know we can win there but, obviously, it makes it a bit more difficult,' Lampard said.
'Ideally, you get a result at home, in front of your home fans. But it wasn't to be. So we've made it a must to go and win there.'
United have never lost a European tie after winning the first leg away from home.
Lampard added: 'People will make Man United favourites and probably rightly so, considering they've won at our place.
'But we're certainly still in the game and we've got a belief in ourselves that we can go there and win.'
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