Roberto Di Matteo's men are currently four points ahead of Manchester United and one point clear of Manchester City, meaning a win for the London club will keep them out of sight from their title-contesting rivals.
However, despite the current leaders being undefeated so far in the League, Sir Alex reckons this isn't the best Chelsea side he has seen.
He told reporters: “I wouldn’t say this is the strongest Chelsea team. I think if you go back to [Jose] Mourinho’s, they were formidable, and really difficult to play against.
“That period of Didier Drogba, a younger John Terry and Frank Lampard, who one year got 30 goals from midfield – they’ll never get that again. They were a really powerful team, hard to beat – and ruthless.”Terry will have to watch the action from the sidelines whilst serving the second game of his four-match ban, while Lampard has been ruled out of the game due to an injury he picked up in the Champions League group-stage match in midweek.
Even though United will not face the 'ruthless' Terry and Lampard, Sir Alex understands the attacking threats Roberto Di Matteo can deploy against his defence.
The 70-year-old Scot continued: “They gained confidence from winning the Champions League, but Roberto has shown he’s bold and you’ve got to give the lad credit. It’s very positive.
“I thought it was a risk to have those three players [Juan Mata, Oscar and Eden Hazard] in the same team. Attacking-wise he’s got great options.
“But if you can contain them you have a chance.”
Chelsea host Manchester United on Sunday afternoon.