Sharethematch.com ambassador Andy Gray was talking exclusively to tribalfootball.com
If United were losing goals from set-plays then he could sort it, if they were losing goals from crosses then he could iron those mistakes out, and if they were conceding from counter-attacks then he could correct the problem.
But at the moment United are letting in goals of every type and therefore it becomes very difficult to put your finger on one thing.
All you have to do is keep playing, keep working hard on the training ground, keep doing lots of shadow work, moving and working the defence.
They're all good going forward but defensively none of them are anywhere near playing the way they would like to when they don't have the ball.
One positive for United though will have been Javier Hernandez getting two goals - he's definitely given Sir Alex a dilemma.
I think they will go with something like that but the problem Sir Alex will have is that when he plays that diamond it gives him the option of playing two up front and giving Van Persie a strike partner with Rooney a bit deeper.
That strike partner has been Danny Welbeck in recent games and it might be Hernandez this time.
But sometimes because a player has a good game one week you can make the mistake of playing him again in the next game.
We saw that from Roberto Mancini picking Edin Dzeko against Ajax - he scored two for Manchester City against West Brom but that was never going to necessarily compute into him having a good game in Amsterdam on Wednesday, and he was very poor.
It's a nice problem for Sir Alex to have and I look forward to seeing what system he picks at the weekend because if he goes in with a diamond it could prove to be revolutionary for him.
In the 26 years he's been there, he's always been a manager who has had wide players in his team.
United haven't won at Stamford Bridge in the league for ten years, but whether they can finally break that sequence I'm not sure because this is a tough one to call.
The result last year was 3-3 after an amazing comeback from three down by United, in a game that they looked totally out of.
It wouldn't surprise me if it was a scoring draw again. I expect both teams to score simply because defensively neither of them are at their best and offensively they've both got some wonderful players.
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