Roy Keane has warned Manchester United's title rivals that his former club will "only get stronger".
Keane said United were "red hot favourites" for the Premier League and believes only an injury to Wayne Rooney could pose a serious problem.
Ahead of Chelsea's visit to Old Trafford on Sunday, Keane correctly predicted that his former side would prevail against their London rivals.
But the former Ireland captain did praise Blues manager Andre Villas-Boas.
Keane, 40, who was sacked as Ipswich manager in January after 20 months in charge, told BBC Radio 5 live's Sportsweek: "United to me are just going to get stronger and they are the team to beat as usual.
"At reserve and academy level, they have got such good young players coming through.
"Eventually you hope they get into the first team, just as Danny Welbeck and Tom Cleverley have.
"And they settle straight into the team because they've got good habits, good attitudes and a good spirit.
"The only major question mark would be if Wayne Rooney picks up an injury, because he's a big, big player for them.
"He is scoring goals for fun. Since he signed his contract, he has settled down and his best years are still ahead of him."
With the two Manchester clubs scoring so freely in their first few Premier League games, Chelsea have rather been in their shadow so far, but they are unbeaten and just two points behind United and City.
And Keane says he has been impressed with new Chelsea manager Villas-Boas.
"I like him," he said. "I think he's going to do a good job down there.
"I think the [Juan] Mata signing was a massive signing, because there was a lot of talk that things had gone flat.
"I think it's suiting them that United and City are grabbing all the headlines.
"I've said before the biggest danger to Chelsea always seems to be that self-destruct button among their own players.
"There are massive egos with that bunch."
Keane explained why he thought United would beat Chelsea on Sunday: "I always look at United and, even if they are not at their best, they seem to get results.
"I certainly can't see them getting beaten today, but it will be their first big test."
Keane also said he was ready for a return to management: "I am enjoying my break but football's in my blood and I hope to get back into at some point.
"If an opportunity comes up in the next few months, I will be ready for it.
"I am only 40. If chairmen and chief executives do their homework I'm sure I have a chance."