The Red Devils' catastrophic season lurches from one disaster to the next, with Moyes' side unable to come through what was previously billed as a favourable tie.
Goals from Alejandro Dominguez and Arsenal loanee Joel Campbell have left United with an uphill task for the second leg, with progression in the tournament vitally important as Moyes' men look unlikely to qualify for the Champions League next season.
The former Everton boss was clearly shocked at the display as he spoke to the press after the game.
“It's the worst we've played in Europe [this season], that's for sure,” said Moyes in his post-match press conference. "It was a really poor performance. We didn't get going from the start. We didn't deserve anything from tonight.
"We just never got to grips with things. To a man, you could hardly pick anyone out [who played well]. We just didn't perform well.
“I'm surprised. I didn't see that level of performance coming. We came into the game in good form and a good mindset but it didn't show tonight.
Moyes' comments that nobody played well last night could be a huge indication of who will be part of the plans at Old Trafford next season, with a big overhaul planned. Of the line up from last night's game, it would appear that only David de Gea, Wayne Rooney and Robin van Persie will be considered key players next season, and Roy Keane stated after the game that United need six new players this summer.
Youngster Adnan Janzuaj and substitute Marouane Fellaini would be expected to contribute heavily next season, whilst Juan Mata was cup-tied, but the rest of the team appears to be up in the air - so who could Moyes let go in the summer?
Experienced trio Patrice Evra, Rio Ferdinand and Nemanja Vidic look poised to leave the club, meaning Moyes will have to bring in two new centre backs as well as a new left back, whilst sporadic runs for Rafael, Chris Smalling and Phil Jones at right back have yet to yield any rewards, so a sturdier right back could also be targeted, leaving Moyes to work with a totally new defence.
Michael Carrick has come in for plenty of criticism lately, and so has his midfield partner Tom Cleverley. With another poor showing tonight and rumours of a move for Barcelona's Alex Song, could Moyes be looking to pair the Cameroonian with Fellaini in a powerful midfield combination?
The play of Antonio Valencia and Ashley Young has been poor for some time now, and it was on show again against Olympiacos. Whilst Januzaj has impressed and Mata is still settling in, a natural winger is needed to be able to widen the pitch, and Young, Valencia and even Nani could all be sold to bring in more consistent replacements.
NWith all that in mind - and the possibility of a striker coming in to replace Javier Hernandez - Moyes may just need more than the six players Keane predicted, and his comments last night suggest that his patience may be running out with his group of underachievers.
image: © Jenny Leigh