The way Carrick played against Olympiacos was, pretty much, like a destroyer. He did a good job winning the ball back from the opposition, but he just sat deep and rarely ventured forward. That would have been fine had he had options to pass to, but against Olympiacos, everyone was far away from Carrick and/or not willing to receive the ball from him. Valencia almost always lost the ball whenever he was pressed by Holebas, so Carrick stopped giving the ball to him unless he was clearly open whilst next to the touchline. Young was playing fairly safe when on the ball even though his movement and positioning in the first half was decent (the second half was dreadful from him, however). Rooney and van Persie were too far away for Carrick to play at a fast tempo, and once Rooney started to drop deep, Olympiacos were settled into their shape, and no one else made themselves available for the ball. Cleverley was too passive to play in central midfield, of course. Even if he made himself available, he didn't assert himself on the pitch and had the attitude of a bus passenger.
There were so many instances when I saw Carrick receive the ball with no one getting into the gaps in the middle for him to pass to. Carrick, of course, didn't take risks by passing to players who were already closed down (instructions from Moyes and the coaches, maybe?), so he played passively, on the ball. Compare that to last season, when he was more adventurous with players positioning themselves better than nowadays.
One can blame Carrick for being passive and gutless, but if his options aren't readily available, and he gave the ball to them only for the opposition to win it back quickly (as was the case with Valencia), Carrick would have been criticised for not passing it to the right players.