With Manchester United sitting seven points clear in the Premier League as they look to retain their title and safely through to the knockout phase of the Champions League, it appears hard to argue with Sir Alex Ferguson’s logic that he doesn't need to enter the transfer market this month.

However, look a little deeper and it is easy to see that United have looked vulnerable for much of the season. You have to go down to 12th place to find a team that has conceded more goals in the Premier League this season than United and they have already came from behind to win eight league games.

If, as he has a penchant for doing, Ferguson is merely being coy with the media about his intentions, here are five players that he might want to target in the transfer window:

Victor Wanyama (Celtic)
Manchester United’s most glaring weakness, as it has been for several seasons, is in central midfield. Michael Carrick has had some fabulous moments this campaign, but without a more dynamic presence alongside him he can often get overrun against the better teams. A potential partnership between Carrick and Celtic’s Wanyama would be intriguing.

The Kenyan, who was linked to United in the summer, has really come to the fore this season in the Champions League, particularly in Celtic’s victory over Barcelona. Celtic boss Neil Lennon has said that he values the 21-year-old at £25 million, although he could be available for significantly less. Perhaps the main stumbling block to any deal is that Wanyama would be cup-tied for the Champions League.

Kevin Strootman (PSV Eindhoven)
Another player who could offer complimentary skills to United’s midfield is highly-rated Netherlands international Strootman. Talk of United’s interest in the PSV Eindhoven captain has been incessant for at least the past year.

The suggestions are that the 22-year-old will remain in the Netherlands until the end of the season, although an offer in excess of £20 million may be enough to change that.

Wilfried Zaha (Crystal Palace)
The reports are that Manchester United are locked in a battle with Arsenal, Chelsea and Tottenham for the Crystal Palace winger. With the 20-year-old earning rave reviews for his performances this season and already having earned a first cap for England, it is easy to see why such illustrious clubs are interested in Ivory-Coast born Zaha.

Strengthening their attacking options would not appear to be a priority for United, but with Nani seemingly unsettled and perhaps soon to depart, Zaha would offer another option out wide. It appears, though, that even if Zaha is sold in January he will remain at Palace for the rest of the season.

Leighton Baines (Everton)
Patrice Evra continues to be a useful contributor going forward as his four goals in the Premier League demonstrate, but he is also becoming an increasing liability defensively. The 31-year-old has been directly or indirectly responsible for the concession of several goals and it may be that his time as a first-choice is coming to an end.

United were strongly linked to Leighton Baines in the summer before reportedly being dissuaded by Everton’s asking price. But, as Baines continues to demonstrate himself to be among the finest left-backs in the Premier League, Ferguson may be encouraged to push the boat out to sign the England international this month.

Mapou Yanga-Mbiwa (Montpellier)
The Montpellier captain has said that one of his dreams for the year ahead is to play for Manchester United. It might be wise for Ferguson to make the 23-year-old’s wish come true. After leading his side to their first ever Ligue 1 title last season, Yanga-Mbiwa has now established himself as a regular in the France team.

Central defense is an area where United have several options, although there are currently doubts about each one. Rio Ferdinand is now aged 34 and will be out of contract in the summer, while 31-year-old Nemanja Vidic is still recovering from a second serious injury in the space of 12 months. Meanwhile, the three younger options—Jonny Evans, Chris Smalling and Phil Jones—have yet to completely convince at the very highest level. Yanga-Mbiwa looks to have the all-round ability to be able to come in and make an immediate impact.