David Moyes wanted a midfielder and a left-back this summer.
But he failed to land a full-back, missing out with bids for both Fabio Coentrao and Leighton Baines.
With Patrice Evra turning 33 before the season is out and Alex Buttner failing to prove he's a viable long-term replacement, Moyes is expected to go back into the transfer market, either in January or next summer.
January moves are complicated by the Champions League because Moyes is unlikely to want to sign a cup-tied player if United are still in the competition.
But here's a list of left-backs for Moyes to potentially pursue in January.
They're listed in order of the likelihood of arriving at Old Trafford in the next transfer window, with consideration given to the player's desire to leave and the club's willingness to sell.