Nemanja Vidic's decision to leave Old Trafford is a crushing blow for David Moyes and with Rio Ferdinand also expected to retire, Manchester United are going to need a whole new back four next season.
Vidic is going to be incredibly difficult to replace and, alongside Ferdinand, has formed undoubtedly one of the greatest centre-back partnerships in the Premier League. A future without them both is a grim prospect for United.
This was supposed to be the season of transition for Moyes but I fear he has got to not just replace his two centre-halves this summer but find an entirely new defence.
The Rio Ferdinands and Vidics of this world only come along so often and if you're a Premier League manager, there's really nobody that good you can go out there and buy.
Centre-half is certainly the one position where is there is a complete of dearth of quality, not just in English football but across Europe. The demand far outweighs the supply. To lose two at the same time is a nightmare scenario for United and Moyes.
Phil Jones and Chris Smalling are the players seen as United's future but it really has not happened for them. If they are the future, then it is going to be an uncertain future, without a shadow of a doubt.
United have said Vidic's decision was by mutual consent but I'm not so sure. While he is not running away from the situation, I think he has realised that he simply cannot play in English football week in, week out any more.
This season he has not made that many appearances and that tells its own story. He has had a long stream of injuries, he doesn't train a lot and you can tell he has been struggling.
When your team are struggling, you need your best players out there but Vidic has not been able to play. It's not as if he is 25 any more, he will be 33 in October, and he's arguably taking the easy option.
It is probably at the back of his mind, 'I've had a great run here but I'm not going to play every week next season'. He will want to go and play in a league where the pace of the game is slower, like in Serie A.
Ferdinand will probably retire at the end of the season while Patrice Evra will definitely go. Evra has been causing so many problems on the field this season, and has been at fault for so many goals, his best days are behind him.
Alexander Buttner certainly isn't the answer as a replacement, either in the short-term or long-term.
Rafael is not the answer at right-back either. He has always been seen as quite impetuous and, as you saw against Fulham yesterday, he is not great in possession and has not come on as well as they had hoped.
It all depends on what Moyes does. Will he be tempted to go with Smalling, Jones and Rafael? In my opinion, that is taking a big chance and I don't think he can afford to do that.
The chances are that you would be having another difficult season like the one they're having at the minute. You look at the United personnel and who have they got?
Is Smalling a right-back or a centre-half? I don't think he's great in either position. Jones plays in midfield and defence and is yet to settle on one.
Jonny Evans is okay if he has got a Vidic in his prime alongside him but without that experience and assurance, I am not so sure he can handle it.
You have got to have a partnership at centre-half, you have got to bed them in like Ferdinand and Vidic. When you are winning and scoring four of five goals, it is so much easier to play but when you're struggling, there's no hiding place and you get caught out.
But if you get the partnership wrong it can be catastrophic. That's why you need six months to a year to get them playing together so they can build an understanding.
Replacing Vidic and Ferdinand is going to be one of Moyes' biggest challenges. In England, you have got John Terry and Vincent Kompany as the two outstanding centre-halves but after them you would have to ask, where are they?
It is certainly a massive problem, not just for United, but any of the big clubs in Europe.
While Vidic has been an outstanding servant for United, there is no doubt he was at fault for both Fulham goals in what was a crazy game.
Evra was also culpable for the first goal but Vidic was poor leaving his position.
For most of the game he was really good in the air, aggressive, winning everything and ploughing through people.
The back headers to the goalkeeper were totally assured but then in the 94th minute, he tried to cushion a header to Michael Carrick that was never really on and Carrick had nowhere to go.
Quite simply, Vidic has cost them two points. It has not happened too often in his career at United and whatever happens until the end of the season he will be remembered as one of the club's legends.
But replacing him, and Ferdinand, is going to be a huge ask. (© Daily Telegraph, London)