The problem is that we don't really have a left-winger of any actual quality. Nani is very inconsistent and you can count the number of times on one hand he's actually ran the show, Giggs no longer has the pace to dominate the line making our best option as Park, who seldom loses the ball, but doesn't really beat people and make crosses, his game is more naturally based around being in the middle and making neat passes. Personally I'd go for a personal pet-hate of mine and play a wing-back on the wing and play Fabio there, we already know he can do the dirty work of tracking back, but can dribble and has the pace to beat anyone out there, but again, wing-backs are wing-backs for a reason, usually because they can't play on the wing, but it may be the best temporary solution.
Saying that, Macheda usually plays on the left when he has played and he's done a good job there, but again, he's not a winger by nature. We do need someone who can run the left hand side of the pitch well.
