What will be so concerning for David Moyes's side is that the scoreline was an accurate reflection of the contest- United were dominated by a side that recently sold its leading scorer Kostas Mitroglou to Fulham and whose second leading scorer Javier Saviola was out with an injury.
United's lack of midfield creativity was exposed yet again. Juan Mata is cup tied with Chelsea and therefore ineligible so Moyes opted for two natural wingers in Ashley Young and Antonio Valencia in the wide midfield positions in his 4-2-3-1. Unlike a number of modern wide players that often tuck inside to receive passes between the lines, Young and Valencia keep wide positions and tend to receive the ball near the touch lines. This was an issue for United today because Olympiakos pressed excellently in midfield. Olympiakos also played a 4-2-3-1 so the battle was 3 v. 3 in midfield. Alejandro Dominguez and Giannis Maniatis pressed United's two holding midfielders Michael Carrick and Tom Cleverley while Delvin Ndinga sat just in front of the back four and checked the runs of Wayne Rooney- who was playing the #10 off of Robin Van Persie- between the lines. With Young and Valencia maintaining wide positions, it made Ndinga's job tracking the movement of Rooney less difficult than it should have been because he only ever had Rooney to worry about in central areas. Had a player like Shinji Kagawa started on the left he'd have tucked in field towards Rooney to allow United to overload the midfield in Ndinga's central zone.
With Ndinga being allowed to closely track Rooney without having to worry about Young or Valencia tucking inside to receive possession either side of him, United had no forward passing options when they had the ball in deep positions. The pressing of Dominguez and Mantiatis on Cleverley and Carrick forced the two United holding midfielders into making hurried decisions- they could either go backwards or loft hopeful straight balls into the final third. Much has been made about the lack of quality in the middle of midfield for United and this performance will do little to silence those assertions- Carrick got on the ball plenty but wasn't able to dictate the pace of the game and Cleverley made too many poor passes and was dispossessed too frequently. Carrick completed 89 passes but only 12 of those were into the attacking third.
Olympiakos won't get enough credit for how well they pressed in midfield but it shouldn't have been quite so easy for them. Moyes certainly needs to spend money on a deeper midfielder to pair with Carrick but he's also making questionable tactical decisions. The inclusion of Kagawa would have made United more dynamic in the final third. He's good at tucking in from the flanks and positioning himself in dagerous pockets of space and has the quality to unlock a defense with his final ball. United were simply too rigid with Young and Valencia in the squad and were made to pay.