That's according to Red legend Jamie Carragher.
Manchester City was imperious on its way to the glory of the Premier League last season, but with all the major teams strengthening this summer, this season could be the most unpredictable title race of recent years.
Both Chelsea and Arsenal have added new faces and are under new guidance this term.
Maurizio Sarri has been entrusted with the task of guiding the Blues back to the first four places, while Unai Emery has great shoes to fill in the Emirates.
"United seems like fuel".
Liverpool legend Jamie Carragher
United had a winning start last night against Leicester, but José Mourinho has been frustrated by the lack of transfer activity.
The 2-1 success over the Foxes may have clouded the cracks and Carragher is concerned about Mourinho's tendency to turn on his players.
Tottenham failed to attract anyone during the transfer period and may face a complicated start to the season with many of his squads still recovering from the World Cup.
Carragher has backed City to retain his crown and admits that anything could happen in the race for the first four.
"Chelsea has been the master of the trophies immediately after a change of management," he told the Telegraph.
"But they will need time to adapt to a new style under Maurizio Sarri, even though they have also flexed their financial strength in recent days.
"Arsenal also needs time under Unai Emery, a year from now both will be stronger.
"You can never read too much in the preseason, but United seems like fuel.
"It seems that there are problems behind the scenes at Old Trafford, with many missed transfer goals: you never know where it will lead when José Mourinho starts criticizing his own board and players.
"The question for the Spurs is: will they have a hangover in the World Cup?" Nine of their players reached the final stages.
"They have kept their best team together, but the demands of the World Cup make it more surprising that they have not added to their squad."
The Premier League continues today as the Spurs visit Newcastle before Chelsea faces Huddersfield.