Manchester United boss Sir Alex Ferguson admits Chelsea's form slide has stunned him.
Carlo Ancelotti's side lost their way after a rampant start to the season, leaving only United and Arsenal as realistic contenders.
Many blamed the sacking of assistant boss Ray Wilkins for destabilising Chelsea.
Fergie said: "They seemed to get a lot of criticism and maybe that affected them. It will be difficult for them to win the league now. It's not impossible, as we experienced in 1998 when we dropped 12 points to Arsenal, and in 1996, when we came from 12 points behind Newcastle to win it.
"But at the start of the season I could never have envisaged having such a lead over Chelsea. We've found in the past seven years going to Chelsea - we haven't beaten them."
