Manchester United manager Alex Ferguson has admitted for the first time that "noisy neighbours" Manchester City can no longer be ignored at Old Trafford.
"There was a period not so long ago when they were actually in the second division. They were never a thorn in our flesh," said Ferguson.
"Every year, we have had to contend with Arsenal, Chelsea or Liverpool. Nothing changes, one of them will always be a thorn in our flesh because you cannot change history.
"But it (success) takes the pressure off the manager and gives confidence to the players. We have experienced that ourselves and we expect them (City) to be challengers next year. Winning a trophy does a power of good," Ferguson was quoted as saying by The Daily Telegraph.
City's new found financial power will keep them in the title race but the last seven Premier Leagues have been won by either United or Chelsea.
Ferguson expects a stiff challenge from Chelsea, who have a young and a comparatively inexperienced coach in Andre Villas-Boas, who arrived from Porto.
Ferguson said it was a "bold" appointment.
"But I think Abramovich likes to do that. He had Jose Mourinho and maybe he's trying to go back to that. You never knew whether Jose could do it at the time, but he proved a man of his time really, didn't he? But it was a surprise because he [Villas-Boas] is just a young lad. I started at 32, but all I had was a physio.
"The difference now is that he (Villas-Boas) can choose a staff of whatever he wants and that will help him. He's also got a lot of experienced players. Chelsea have got the most experienced side in the league with the number of older players they have got, with (Didier) Drogba, (John) Terry, (Frank) Lampard, (Petr) Cech, (Ashley) Cole," he said.