Manchester United are missing out on more than £26 million a season in potential revenue for Old Trafford's naming rights, according to corporate finance advisors Duff & Phelps.
That figure, which is £7m more than Manchester City earn from Etihad's sponsorship of their ground, is contained in a new study of naming rights values in the Premier League.
Duff & Phelps believes the value of this market has risen by 80 percent from £74.6m in 2013 to £135.6million last year, with the league's 'big six' accounting for more than three quarters of that sum.
United, however, have repeatedly said they have no intention of selling the naming rights to their 75,000-capacity home, a stance that sources have told Press Association Sport has not changed.
The study ranks Chelsea's Stamford Bridge as the third-most valuable naming rights deal at nearly £18m a year, with Spurs' new White Hart Lane worth a potential £15.5m to a sponsor -- marginally more than Emirates' deal with Arsenal.
Liverpool's Anfield is in sixth place at £11.1m, but this is probably a reflection of the fact the naming rights to famous old grounds are not particularly attractive to sponsors as very few people ever use the new names -- a point that could also be made about Old Trafford.
The evidence from North America, where naming-rights deals are common, suggests sponsors are also reluctant to take on a ground that has previously been sponsored by somebody else, as the name tends to linger. This explains why new stadia, whose names have not yet stuck, are worth a premium.
Speaking to Press Association Sport, head of UK sports at Duff & Phelps Trevor Birch acknowledged that these valuations were "not an exact science'' and were "potential, theoretic valuations that might not be achievable on the market.''
But the former Liverpool youth player who quit football to train as an accountant and went on to become chief executive at Chelsea, Leeds, Everton, Derby, Sheffield United and Portsmouth, believes the naming rights to "iconic'' grounds, such as Old Trafford, can still attract big sums.
Birch highlighted the example of Real Madrid and the Bernabeu -- although that deal, worth a reported £350m with energy multinational Cespa, is now in doubt -- and pointed out that eight of the 20 clubs in the Premier League have got naming-rights deals.
"It's an emotive topic, particularly in this country, but it's an area that is definitely under-utilised as a revenue stream,'' Birch said.
One Premier League club keen to tap into this market is West Ham, but efforts to secure a naming-rights partner for the London Stadium have been hampered by negative headlines related to its building and running costs. Duff & Phelps believes sponsorship for the former Olympic Stadium could be worth almost £5m a season, though.