Alan Hansen: Time for Moyes to decide if Van Persie is worth all the trouble
That is being borne out by the problem they now face with Robin van Persie.
Just when David Moyes should be looking forward to a clear week before the crucial game against Liverpool next Sunday, Van Persie's reaction to being substituted during the win at West Bromwich Albion ensures that everyone is now focusing on him and his future at Old Trafford.
It has presented Moyes with an amazingly difficult situation, one in which there can be no winners, but the reality is that the persistent speculation surrounding Van Persie is an indictment of the modern game.
It is too easy now for players to allow dissatisfaction and unhappiness to emerge, either through social media or a quiet word here or there with the intention of it eventually seeping out before being denied.
And when the only response to losing badly against Olympiakos should have been to keep schtum and get on with it, Van Persie instead chose to speak to a Dutch television station to complain about team-mates occupying the same space as him on the pitch.
With Van Persie, it appears that there is no smoke without fire and the doubt surrounding one of his star players is the last thing that Moyes needs right now.
When you are struggling and looking for results to turn the corner, unity is key.
There is no way you will get to where you want be, though, if one of the first names on the team-sheet is constantly being linked with a move away or is showing signs of dissent.
Dealing with it is much more difficult for Moyes than it would have been for his predecessor, Alex Ferguson, however.
Because Ferguson had seen it, done it and won it all several times over, he earned himself the leeway to make a mistake.
It is easy to make those decisions when you are nine points clear at the top of the table, but a totally different scenario when you are sitting in sixth position, nine points adrift of a Champions League place.
Moyes could decide to sell Van Persie in the summer or he could instead choose to keep him, work with him and hope that any problems can be resolved.
But having sanctioned a new contract for Rooney, United and Moyes have a dilemma with Van Persie that has no ideal solution.
If they sell him, and let him follow Nemanja Vidic out of the door this summer, who do they sign to replace him?
But if Van Persie is truly unhappy and needs to be convinced that his future is at United, then the club may to have to sugar-coat it because of the contract they gave to Rooney.
Van Persie will undoubtedly already be earning stupendous money at United, but if he has seen his fellow striker secure a new contract on better money, it is only human nature to want X if the other guy is getting Y.
Without Van Persie, there would have been no title for United last season and he will know that his goals made the difference when Rooney was having his problems with Ferguson 12 months ago.
So United may have to ask themselves whether they can afford to indulge Van Persie in order to keep him at the club if they decide against selling him.
Financially, they can afford to do that, but they will be giving themselves a bigger problem down the line if they reward a guy who will be 31 this year, one who has had injury problems, with a better contract simply to make him happy.
What message would that send to a 25-year-old in the dressing-room who is earning less than half of Rooney or Van Persie's salary, but has become a key figure in the team?
It would open the floodgates for everybody to knock on the door demanding a pay rise.
It is not a black or white decision for Moyes, though, because, if you take Van Persie out of the equation, where do the goals come from?
If you are looking for a bit of pace or magic to get you a goal, he might not provide it, but he is the only one in the 18-yard box and the alternatives, such as Danny Welbeck and Javier Hernandez, are not what you would call potent forces.
United need everybody pulling for one common cause, however, and all of the noises around Van Persie are currently to the detriment of the team.
When everything was going well last season, there were no hints of unhappiness or efforts to move away, but then you only truly find out about people when things are going badly.
Moyes and United need Van Persie more than ever right now, but the negatives are being outweighed by the positives. (© Daily Telegraph, London)