Unbeaten Manchester United travel to Stamford Bridge fresh from a 1-0 home win over Arsenal that sent them two points clear at the top of the table.
Chelsea, meanwhile, have struggled for form recently and Ferguson has seized on the chance to turn up the pressure on Carlo Ancelotti and his cut-down squad.
Size DOES matter, Carlo: Ferguson believes Ancelotti is struggling after losing experienced players in the summer
Asked on American radio station Sirius XM if Chelsea had let too many players go in the summer, Ferguson said: 'I think Chelsea have been gradually introducing one or two younger players into their squad, so maybe that's why (results have been erratic).
'Michael Ballack's contract came to the end. (Juliano) Belletti's contract came to an end. They have been replacing these players with younger ones such as (Daniel) Sturridge and the young boy (Josh) McEachran.
'Their plan was always to start introducing younger players and I think that's a good thing but it can backfire if you get injuries.
Mind games: Sir Alex says he can'twait for Sunday's match
'You need big squads these days because the number of matches and the intensity of them does produce injuries. There's no question that having a big squad helps.'
Chelsea have struggled recently in the absence of experienced players like Frank Lampard, who has been injured, while star men John Terry and Didier Drogba have also had to play while not fully fit.
But United have continued to grind out results, with players like winger Nani and striker Dimitar Berbatov making up for Wayne Rooney's poor form and injuries.
Ferguson added: 'This is a massive game now. We used to have a terrific record at Chelsea but we haven't won there for eight years. But we'll be ready for it. We couldn't get there sooner.'
Former Chelsea defender Frank Leboeuf has written off his former club's chances of winning the league this season and insisted there needs to be a major squad overhaul at Stamford Bridge in the summer.
Leboeuf, who dismissed talk that Chelsea's draw with Tottenham last Sunday marked the end of their shocking run, said: 'I don't agree this is the turning point for their season. It is hard for me to criticise my former club but I said at the beginning of the season I didn't think they would win the championship.
Shocking: Former Chelsea favourite Frank Leboeuf believes out-of-sorts Chelsea are nowhere near reaching a turning point
'I love them but I really feel they are at the end of the cycle. When I saw them flying at the top, I wondered if I knew anything about football any more but now we are seeing the truth and reality of that club and those players.
'At the end of the season they will need to sell and buy players. They didn't have a bad game against Spurs but one or two years ago they would have won that match. I really feel Chelsea are not Chelsea any more. I am sad about that.'
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