Sir Alex Ferguson is wary of the threat posed by Arsenal ahead of their clash at Old Trafford on Saturday.
While the games between the heavyweights were once seen as title deciders, Arsenal have fallen off the Premier League pace in recent years.
But Ferguson is not under-estimating Arsene Wenger's team, particularly after their scintillating start to the campaign.
This has included a 6-1 hammering of Everton at Goodison Park on the opening day of the season, as well as the 5-1 aggregate victory over Celtic in the UEFA Champions League.
Ferguson said: "Games against Arsenal are always enjoyable and very interesting. At the start of the season there have been some highlights for Arsenal already.
"Their 6-1 win at Everton was an amazing result. I've never known Everton concede that many goals at home before. I can't remember that happening before.
"It's been a good start for them. We've got a game on our hands. We've got to get our form right and make sure it is consistent.
We've lost one game already and can't afford to lose another."
While Ferguson believes the characters of the teams have changed, it will be just as competitive.
He added: "Over the years Manchester United versus Arsenal games were the feature of the Premier League, there's no doubt about that.
"It was the number one game. Some of them were very, very feisty. But the characters of the teams have changed. There is no (Roy) Keane or (Patrick) Vieira, both volatile characters and dominant players.
"I think the personalities of the teams has changed. It will be no less competitive though, just a different type of game.
"There are 35 games left so you can't say it will mean a lot (in terms of the outcome of the title). But we dropped points against the top four teams last season and that's an area I want to see us address."
Wenger sold Emmanuel Adebayor and Kolo Toure to Manchester City this summer, leading some to write the Gunners off.
But Ferguson respects his counterpart's dealings in the transfer market.
He said: "I couldn't understand people writing Arsenal off. I think it was a media thing. I can't see it.
"They have respect and the one thing Arsene has done well is he's always sold a player at the right time. He knows when it's the right time for a player to leave.
"But I don't think the level of their ability has changed one bit."