Roberto Di Matteoâ€™s side have set an ominous pace at the top of the league but Ferguson contends they cannot match the â€śruthlessnessâ€ť of the Mourinho-led Chelsea that won the title in 2005 and 2006, forcing the Scot to raise his own game at Old Trafford.
Ferguson declared: â€śI wouldnâ€™t say this is the strongest Chelsea team. I think if you go back to Mourinhoâ€™s, they were Âformidable, and really difficult to play against.
â€śThat period of Didier Drogba, a younger John Terry and Frank Lampard, who one year got 30 goals from midfield â€“ theyâ€™ll never get that again. They were a really powerful team, hard to beat â€“ and ruthless.â€ť