Ole Gunnar Solskjaer says Manchester United need to harness the spirit of Paris Saint-Germain and put in a "perfect performance" if they are to overcome Manchester City and reach the League Cup final.
United face an uphill battle after losing the first leg of their semi-final against Pep Guardiola's men 3-1 at Old Trafford.
Marcus Rashford's goal gives United a glimmer of hope heading to the Etihad Stadium on Wednesday and Solskjaer said the stunning comeback win against PSG in the Champions League last March can be an inspiration.
United were 2-0 down after the first leg and then 3-1 down on aggregate in Paris before storming back to win on away goals.
"Well, it looked like it was over at half-time," he said, referring to the first leg of the City match. "I have to say the second part of that first half, they outplayed us for a while and it's hard.
"But then when we got the goal, of course you're back in it, we hope for another one.
"But now we've got to go into the memory bank and think PSG because we've done it against good teams before and it gives us some hope, and the game in December (when United won 2-1 against City) of course gives us hope that we can do something there."
Solskjaer confirmed Nemanja Matic is a doubt for the second leg in a press conference that included plenty of transfer talk but no updates.
Sporting midfielder Bruno Fernandes reportedly remains a target for the club, while a number of enquiries have been made as United look at possible attacking options.
Alexis Sanchez would have been an option but does not have a recall clause in his loan deal, although Solskjaer expects him to have an Old Trafford future when he returns from Inter Milan at the end of the season.
"We've got players here we're working hard to get back as well and if there is something out there, then the club are pursuing that and looking at it," said the United boss.
"Of course it is a difficult window. It always has been. I can't remember how many good ones we've brought in, good deals that we've brought in in January. Henrik (Larsson) was good, Nemanja (Vidic) and Patrice (Evra) were two good ones."
When January 2018 signing Sanchez was mentioned, Solskjaer said: "It's very hard because the clubs don't want to lose their best players. Alexis will come back in the summer and prove you all wrong."
Solskjaer expects defender Marcos Rojo to stay at Old Trafford despite speculation over a move to former club Estudiantes de la Plata.
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