United must overcome a 2-0 deficit to reach the quarterfinals.
"It's only twice United have done it [come back from a two-goal deficit in the first leg], most recently in 1984 against Barcelona. Robbo got two goals. It's not something that's happened a lot but it's something we'll try to make happen.
"I see the players every day. With the quality they show me, I think they know they can play better," Moyes said. "I have belief in the players and hopefully we can show it. I agree we haven't seen it as often as we'd have liked but hopefully we can show it tomorrow.
"The most important thing right now is the Olympiacos game and to get through into the next round of the competition."
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