Summer transfer window opens but it's the era of player power

The summer transfer window officially opens in England on Friday with Premier League clubs again set to splash the cash while the futures of a selection of out-of-contract stars dominate headlines on the continent.

Clubs in England will have a period of almost 12 weeks, until September 1, to strengthen their squads, although one of the biggest moves has already been announced, with Erling Haaland heading to Manchester City from Borussia Dortmund.

There will be the usual headlines of Premier League sides flexing their financial muscle, with a huge increase in income from overseas rights deals reportedly taking broadcast revenue for the three-year cycle to 2025 over £10 billion ($12.5bn).

With the financial rewards only getting greater, the chances are English clubs will again collectively splash more than £1 billion on transfers, as they have done in the last six summer windows.

Haaland's move will cost City what might be considered a modest sum of £51 million (60 million euros, $63 million) due to the release clause in his contract at Dortmund.

The prolific Norwegian is unlikely to be the most expensive new arrival in England's top flight -- Liverpool and Manchester United are being linked with moves for Uruguayan striker Darwin Nunez, valued at 100 million euros by Benfica.

Yet it is often the transfers happening beyond the Premier League's biggest clubs that confirm just how powerful England's elite have become.

A prime example is Aston Villa, who finished 14th in the season just ended but have already announced the signings of Diego Carlos from Sevilla and Boubacar Kamara from Marseille.

Brazilian defender Diego Carlos will move for a reported £26 million while holding midfielder Kamara -- who has just broken into the France