Frank Lampard wants Chelsea to unleash the burning sense of injustice over their Champions League setback in the second leg at Old Trafford.
Lampard and his team-mates were left fuming after being denied a "blatant" penalty in Wednesday night's 1-0 defeat to Manchester 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.
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."
He added: "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 said: "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.
"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 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."
Lampard's sentiments were echoed by captain John Terry, who claimed he could be banned by UEFA if he said what he really thought about the penalty incident.
Manager Carlo Ancelotti questioned Mallenco's "courage" in failing to award a spot-kick and Terry appeared to feel even more strongly.
But he said: "I think the most frustrating thing for the players is that we can't come out here and be honest about it. We would face possible bans.
"We're seeing players receiving bans left, right and centre for speaking honestly after games.
"You guys lose out, the players can't be honest and we end up walking on eggshells.
"Unfortunately, I can't say more about it but it was a clear penalty."
Terry, who famously missed a penalty in the 2008 final which would have handed Chelsea victory against United, added: "I can 100% see us turning the tie around.
"They know we're still in it and we certainly do as well."
Terry also refused to rule out an even more sensational comeback in the Premier League title race, despite Chelsea falling 11 points behind United - albeit with a game in hand - on Saturday.
He said: "We're also still in the title race - we realise we're many points away but we've got one of the strongest squads in the league and everybody is now fully fit."
