Baggies beware: It's a game of two 54-minute halves when you play at Rovers' muddy Memorial Ground

That's the nightmare scenario facing West Bromwich Albion when they visit Bristol Rovers in the quarter-finals of the FA Cup on Sunday.

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Because the League One side's Memorial Ground pitch - which they share with Bristol Rugby Club - is one of the heaviest surfaces to play on.

And research undertaken by FA Cup sponsors E.ON shows that playing a 90-minute match there is the equivalent of playing 108 minutes on the pristine surfaces of an Old Trafford, Stamford Bridge - or even the Hawthorns.

This means The Pirates are effectively running for 18 minutes longer than their Premier League or Championship counterparts - and their superior fitness has so far resulted in penalty shoot-out victories against Leyton Orient and Fulham as well as a late strike to send out Southampton in round five.

So Baggies be warned ... if you don't score early, you could be heading home with just promotion to concentrate on.

The findings have been released today by E.ON, one of the UK's leading energy companies.

They teamed up with Professor Don Maclaren of Liverpool John Moore's University to analyse exactly how much energy players would use depending on the pitch they played on.

The Memorial Ground surface is known to be less than perfect – a point reiterated by Rovers manager, Paul Trollope last week.

However, any planned pitch improvements may want to be delayed until next season as it's energy-sapping qualities may have drained opponents and acted as the key to Rovers' best FA Cup run for 50 years.

While an average player would run between 10km and 12km during a game, the heavy Rovers surface increases this to the equivalent of 14.5km in terms of the strain it puts on the body.

The necessary energy it takes to get through a 90-minute match would also measure at 7500kj on a heavy, uneven pitch compared to 6300kj on an immaculate playing surface.

They appear to demonstrate greater stamina in FA Cup ties – excelling at the end of games just as opponents start to tire. And the stats bear this out.

• Four of their five FA Cup ties so far have been decided at The Memorial Ground

• In those home ties, Rovers have scored after the 80th minute four times, with two of the games going the full distance to penalty shootouts.

• On both occasions the still sprightly Rovers penalty takers have got the better of their heavy-legged opponents.

Nick Sandham, Retail PR Manger E.ON UK, said: "Rovers deserve great credit for the energy levels they've displayed in their Cup run – perhaps these findings give a small insight into what makes The FA Cup so special."

E.ON is encouraging fans to make simple energy saving changes to help reduce their carbon footprint through the website www.carbonfootyprint.com. It is hoped that the campaign will help reduce the carbon footprint of The FA Cup.