#3 Liverpool

The trio of Mohamed Salah, Sadio Mane and Roberto Firmino are still heavily trusted by manager Jurgen Klopp, although some have recommended that Liverpool's forward line needs to be refreshed.
Salah continues to be one of the best in the world, but there has been a decline in the form of Mane and Firmino recently. Liverpool's acquisition of Diogo Jota last summer proved to be a smart one, and the Portugal international has made a good impact since joining the club.
However, Liverpool have sold Swiss attacker Xherdan Shaqiri to Lyon this summer, and there are doubts as to whether Divock Origi and Takumi Minamino are good enough players to have as backup options. An unfortunate injury to Salah could create huge problems for the Reds.
#2 Manchester City

Unless Manchester City sign a striker this summer, it would be hard to classify their transfer window as a success.
They have added Jack Grealish to the squad, but Manchester City entered the transfer window on the lookout for a striker and are yet to sign one. Harry Kane was their primary transfer target, but Manchester City could not agree a fee with Tottenham Hotspur, and Kane has now officially announced his intention to stay with his current club.
Ferran Torres, Riyad Mahrez, Raheem Sterling and Gabriel Jesus are all excellent forwards, but they are not renowned for their prolific goalscoring. Manchester City were also interested in signing Cristiano Ronaldo, but the Portuguese superstar joined Manchester United instead.
#1 Manchester United

If you had told a Manchester United fan when the transfer window began that the club would sign Cristiano Ronaldo this summer, they would have laughed at you.
Having acquired long-term target Jadon Sancho this summer, it was assumed that Manchester United were no longer focussing on signing attacking reinforcements. And that would have been the case, had Ronaldo not decided to leave Juventus and Manchester City not started talks to sign him.
Manchester United intervened and now they have a stunning attack. Marcus Rashford, Ronaldo, Edinson Cavani, Jadon Sancho, Mason Greenwood, Daniel James and Anthony Martial are among Ole Gunnar Solskjaer's options. Not to mention Bruno Fernandes, who is an undroppable member of the first XI.
Also Read: Ranking the 5 best defenses in the Premier League this season