Manchester city v Manchester United: Robin van Persie can be the sharpshooter to silence the screams The Dutchman could have chosen City, strengthening further their ability to defend the title. But he picked United, coming with a guarantee of goals. United were always vulnerable last season because their goal difference took a hammering at Old Trafford to City on Oct 23. "I keep talking to them about that, about goal difference,"" reflected Ferguson before training at Carrington on Friday. That game changed it for us. We tried to play the history book that day, attacking with 10 men, 3-1 down, crazy. City ripped them apart on the counter, scoring three more times. So Ferguson went to market in the close season. Van Persie failed to score against City last season but his stealthy movement, clinical finishing and telepathic understanding with Wayne Rooney has already brought him 13 goals in 19 games for United (and two in three for Holland). "Van Persie has been unbelievable,"" Ferguson said. "He has 13 goals at the moment and his intelligence and maturity have definitely been an improvement in the attacking side of the game [for United]."" Critics point acerbically to Rooney's return, only five goals in 16 games for United (plus three in two for England), but he assists Van Persie selflessly. Rooney drops off, drifts wide, but is always aware of Van Persie's positioning, always looking to pick his accomplice out. Others also contribute, helping give United such a sharp attack. Javier Hernández has contributed nine in 18 while Danny Welbeck has only one goal in 19 but occasionally is used wide (his three in five for England have come as a centre-forward). This quartet will keep the "goals for"" column constantly being updated. "The best period we ever had with strikers was 98-99 when we had Andy Cole and Dwight Yorke,"" Ferguson said. Yorke's first season was unbelievable. I think he was the best striker in Europe and he and Cole formed this fantastic partnership. But then we had Ole Gunnar Solskjaer and Teddy Sheringham, fantastic players. That was definitely a golden period for United."" Van Persie's advent has given United a foursome almost as awesome. City coveted Van Persie. "You can want to buy one player but it is difficult because the player makes another decision,"" observed Mancini, also pointing to internal tensions with Brian Marwood, the then football administrator who had one eye on Uefa's financial fair play rules. The transfer market is always difficult and we were also in a difficult moment. We changed the CEO, the man who was in charge in that moment. If you are not strong enough you can have some problems in the transfer market. But not now. Now we can work. We have the time now to work well for next year and to improve our team. Our problem for now is to improve our strikers. Mancini noted the superior form of the United collective compared to his group of Agüero, Tévez, Dzeko and Mario Balotelli. "They have scored 10 more goals than us,"" continued Mancini. Our season depends on our strikers. Usually when you have four strikers, two or three of them are not scoring but one is. At the moment we have four strikers who can't score. Mancini's public frustration at not landing Van Persie hardly transmitted a message of confidence in his resident strike-force but in Agüero he can start a quicksilver forward capable of punishing United's uncertain defence. Mancini masterminded home-and-away derby wins last season, albeit assisted by United's naivety at Old Trafford and Ferguson's cautious tactics at the Etihad. Reminded of these setbacks, Ferguson sounded sanguine. "I've never entered into the "revenge" stuff,"" he replied. At this club, you can't enjoy losing to anyone. The consequences of losing a game here is always huge. We are either front page or back page, and when we lose we are front page."" The clear and present danger posed by City quickens the Scot's pulse rate. It's great. Challenges are what we are made of. I've been lucky that in my time here I've been involved in great competitions with individual teams like Liverpool, Arsenal, Chelsea, now City. It's fantastic. No dull moments. That's the great thing about this club: we can accept challenges, we don't run from them. We face them head on and try to improve what we think is necessary. Like bringing in Van Persie. Sunday will show whether that is enough.