Manchester United are forecast to drop to their lowest-ever position in Deloitte's Money League for 2019-20 as Barcelona became only the third team-ever to top the chart.
The Catalan club became the first club to break the €800 million barrier in 2018-19, with a revenue of €840.8m for the campaign. Real Madrid, the 2017-18 leaders, dropped to second with a revenue of €757.3m.
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United were third with €711.5m, but are at risk of losing their position as the highest-ranking Premier League club for 2019-20 as forecasts show failure to qualify for the Champions League could result in their lowest Money League position ever. Manchester City (€610.6m) and Liverpool (€604.7m) are closing in.
Bayern Munich (€660.1m) were fourth, while Paris Saint-Germain (€635.9m) came in fifth. Tottenham (€521.1m) earned their highest-ever ranking of eighth, with Arsenal (€445.6m) having dropped from ninth to 11th.
"The impact of participation and performance in UEFA club competitions on revenue is evident in London and the north west, with the rise of Liverpool, Manchester City and Spurs driven by reaching the Champions League knockout stages," Sports Business group at Deloitte senior manager Sam Boor said.
"The relative decline of Arsenal is a direct result of not participating in the competition for a second consecutive season, a fate that may also befall Manchester United."
Boor also highlighted leaders Barcelona as the club others should follow in order to adapt to football's changing landscape.
"Barca is a clear example of a club adapting to changing market conditions, reducing the reliance on broadcast revenue and focussing on growing revenues within its control," he added.
"The club's commercial operation generated €383.5m of revenue, which is more than the total revenue of the 12th placed club in this year's Money League.
"With the club expecting further growth of €30m in commercial revenues and total revenue of almost €880m in 2019-20 we expect them to retain the top spot in next year's edition. Barca is on course to achieve its stated ambition to be the first €1 billion Money League club in years to come."
Top 20
1. Barcelona €840.8m
2. Real Madrid €757.3m
3. Manchester United €711.5m
4. Bayern Munich €660.1m
5. Paris Saint-Germain €635.9m
6. Manchester City €610.6m
7. Liverpool €604.7m
8. Tottenham €521.1m
9. Chelsea €513.1m
10. Juventus €459.7m
11. Arsenal €445.6m
12. Borussia Dortmund €377.1m
13. Atletico Madrid €367.6m
14. Inter Milan €364.6m
15. Schalke €324.8m
16. Roma €231m
17. Lyon €220.8m
18. West Ham €216.4m
19. Everton €213m
20. Napoli €207.4m