Manchester - Sir Alex Ferguson believes Chelsea are the team that pose the biggest threat to Manchester United's hopes of bringing the Premier League title back to Old Trafford.
Carlo Ancelotti's Chelsea ended United's three-year reign as Premier League champions last season and also won the FA Cup to complete the double.
Ferguson expects big-spending neighbours Manchester City and Tottenham, who finished fourth last season, to progress this term, but the United manager says Chelsea remain his team's biggest rivals.
United will get an early look at Chelsea when they face the Blues at Wembley on Sunday in the Community Shield, which marks the final weekend before the start of the Premier League season.
"They won the league and cup double last season and you can't dismiss them," Ferguson said on Friday.
"It could be a league of a lot dangers in terms that the competition is being raised all the time. Last season the monopoly of the big four was squashed and Tottenham came into it.
"You'd think that Tottenham would make progress this season and Man City have bought again, you obviously have to put them in the equation.
"I think Everton, after all the injury problems they had last season, will come into it also. It's going to be a competitive league, there's no doubt about that.
"It's getting more competitive every season now. But I do think the team that won the league the previous season are the ones you look at. Chelsea have got that experience."
Ferguson has confirmed that Wayne Rooney, back at United after a disappointing World Cup with England, will play at least 45 minutes at Wembley this weekend.
But the Scot believes supporters will not see the best of the forward until well into the season.
"The profile of the World Cup means that it does take a lot out of players," Ferguson said.
"You can't dismiss that in terms of giving them rest and we've done that. We've given them 28 days rest and we'll get the benefit throughout the season.
"I don't think we'll get the benefit of these players (who appeared at the World Cup) until maybe the third week of the season."
Eight days before United start their Premier League campaign at home to Newcastle, Ferguson will send a patched-up side out at Wembley.
Michael Carrick will miss the start of the season after damaging his ankle during a friendly in Ireland on Wednesday.
The England midfielder joins international team-mate Rio Ferdinand and French winger Gabriel Obertan on the treatment table.
Brazilian Anderson, who was involved in a minor car accident a few days ago, will also be absent at Wembley, while Owen Hargreaves is still having his damaged knee assessed in the United States.
In addition, Fabio Da Silva and his brother Rafael are unlikely to feature after suffering a bout of food poisoning earlier in the week.
Patrice Evra, the France full-back, is definitely a non-starter on Sunday after only returned to training on Thursday after the World Cup."