LONDON • Manchester United risk losing their position as England's richest club as a string of management missteps and sub-par performances left them shut out of European football's most lucrative club competition.

After failing to qualify for the Champions League for the second time in four seasons, the Red Devils have forecast that annual revenue will slide as much as 11 per cent from the previous year.

United earned €711.5 million (S$1.06 billion) for the 2018-19 season to take third spot in Deloitte's Money League, behind Barcelona, who top the earnings table on €840.8 million, and Real Madrid, who are second after generating €757.3 million.

If the fall in revenue holds true, United could fall behind Premier League rivals Manchester City and Liverpool this year for the first time since the report was published 23 years ago.

The club are also in peril as both sixth-placed City (€610.6 million) and Liverpool, who are seventh with earnings of €604.7 million, have "talisman managers" in Pep Guardiola and Jurgen Klopp.

According to Alan Switzer, a director in Deloitte's Sports Business Group, they "have combined strong on-pitch performance with investment in stadia and commercial infrastructure to deliver sustained revenue growth".

Dan Jones, a partner in the same Deloitte group, added: "United have been the top English club since we started the Money League, but that could come under pressure when we do it in 2021.

"That will cover this season when Liverpool are having a tremendous season on the pitch, so we think there's a possibility of United losing that No. 1 position.

"Part of that will ride on how the rest of this season goes, if City or Liverpool go deep into the Champions League.

"If you think about where we were 10 years ago, the idea that City would overhaul United in financial terms would have seemed far-fetched."

All three English clubs, however, remain well adrift of La Liga champions Barcelona.

While the Catalan giants are undergoing upheaval on the pitch after firing coach Ernesto Valverde on Monday, they are ahead of the curve when it comes to bringing merchandising and licensing activities in-house.

Jones said: "Barca are a clear example of a club adapting to changing market conditions, reducing the reliance on broadcast revenue and focusing on growing revenues within their control.

"The club's commercial operation generated €383.5 million of revenue, which is more than the total revenue of the 12th-placed club (Borussia Dortmund) in this year's Money League.

"With the club expecting further growth of €30 million in commercial revenues and total revenue of almost €880 million in 2019-20, we expect them to retain the top spot in next year's edition."

Still, Premier League clubs continue to dominate the list, with eight in the top 20, more than any other country, and all the clubs hail from the 'Big Five' leagues of England, France, Germany, Italy and Spain.

AGENCE FRANCE-PRESSE, BLOOMBERG