Not only did Wednesday night mark the end of Manchester United's Champions League campaign for the season, it was also the last time the Old Trafford faithful are likely to see skipper Nemanja Vidic this term.
The Serbian centre half caught his studs in the turf after an innocuous challenge with Marco Streller against Basel and the worst possible scenario was revealed to be true when it emerged that he had ruptured a cruciate knee ligament.
There is no doubt Vidic will be back but with Rio Ferdinand's seemingly constant injury issues, the questionable form of Jonny Evans and the inexperience of Chris Smalling and Phil Jones, Sir Alex Ferguson may look to delve into the January transfer market for defensive reinforcements.
Vidic himself was a January signing, and GiveMeFootball looks at the men who could replace him this winter.
1. Gary Cahill (Bolton Wanderers)
The England international will be in the last six months of his contract by the time the window opens and will be available for a knock-down price. It is almost a given that he will be leaving Bolton and the former Villa man is linked with Chelsea, Tottenham and Arsenal on an almost daily basis.
If the Champions came calling though it may be an ideal move for Cahill who would not have to relocate from the North West.
Although he would not be the most glamourous of signings, Cahill is dependable and has made himself into something of an England regular in the past year replacing either John Terry or Ferdinand when they are unavailable.
Strong in the air, relatively quick and decent on the ball, United could do a lot worse.
2. Jan Vertonghen (Ajax)
A left-footed Belgian international defender who has played with Thomas Vermaelen and Vincent Kompany for his national team, Vertonghen is very good on the ball, takes a mean free-kick and is another player almost certainly available for transfer as he has stated he will not be extending his Ajax contract that ends in 2013.
Once again Spurs and Arsenal are rumoured to be interested in securing his services for around £10 million but United could step in at the eleventh hour to hijack the deal.
His versatility may also impress Sir Alex, as Vertonghen can play at left-back or in holding midfield as well as in the heart of defence, although there has been no speculation in the press as-of-yet that United will be looking to the 24-year-old.
3. Fabricio Colocinni (Newcastle United)
If you had linked the Argentine international to the mighty Manchester United after Colocinni's first season on these shores then people would have thought you were mad. He struggled with the relentless pace and physicality of the Premier League and was part of the Newcastle side that got relegated on the last day of the 2008/09 season.
Perhaps surprisingly he stuck it out for the Championship campaign that saw the Toon army break all kinds of records on their way to the title. Now looking reassured and unflustered, the Magpies captain has been the bedrock of their superb start to the season.
With Newcastle doing so well with such a small squad, it would be strange if they decided to cash in. The Newcastle board have a habit of doing the unexpected and infuriating the fans though, so do not rule out them getting rid of one of the players that has been influential in their superb end to 2011.
4. Brede Hangeland (Fulham)
Near enough since the moment Roy Hodgson brought Brede Hangeland to a struggling Fulham from Copenhagen, the Norway captain has been rumoured to be moving to one of the bigger clubs in the land.
Standing at six feet four and a half inches tall his he is imperious in the air as you would expect, but he also possesses a deceptive turn of pace and is a more than average ball player.
Time may not be on his side however, as he is now 30 years old but for a short-term boost of experience then there may not be many better options on the market.
5. Mats Hummels (Borussia Dortmund)
Probably one of the best centre halves anywhere in Europe last year as unfancied Dortmund won the Bundesliga title, even out shining partner Neven Subotic with his strength, tackling and generally Rolls Royce-like defending.
WIth twelves German caps under his belt in the last two years, he has replaced Per Mertesacker in the national team and looks set to be there for many years to come.
Although he has not impressed quite as much this season, Ferguson would fancy himself to bring the best out of Hummels and at 22 he could be at the heart of United's defence for ten years. Vidic and Ferdinand will not be around forever and Hummels could be the man to take over the mantle, especially if Phil Jones continues to be selected to play in midfield.