How good are Fulham? They are probably the fifth best team in London. They are better than West Ham and Watford. They might even have finished above Crystal Palace if they were in the same division.

The problem is that they are not in the Premier League. They are in the Championship play-offs. Fulham are two games away from the promised land after a four-year exile. The top flight feels tantalisingly close but it could disappear like a mirage very suddenly. The dream could fade as soon as Monday night. Fulham must overturn a 1-0 deficit against Derby in the second leg at Craven Cottage.

Their owner, Shahid Khan, comes from the world of American sport where the golden rule is ‘reach the play-offs’. In the Championship that is often a recipe for disappointment.

Fulham’s 23-game unbeaten run ended on the final day of the campaign with a 3-1 defeat by Birmingham but their dominant performances in 2018 hinted at how good they can become.

They were 12th in the table on New Year’s Day. Never mind the last-day defeat, just a couple more points in the autumn could have secured that coveted automatic promotion spot. On Monday, they must assert themselves. Fulham had more of the ball in the first leg but could not turn possession into supremacy. Patience and a clinical approach will be crucial at the Cottage.

It is the right time for Fulham to go up. Slavisa Jokanovic’s reputation as a manager is growing. The Serb’s style of play is as impressive as his attention to detail. Bigger teams will come calling if he remains in the Championship. There are a number of prominent London clubs who could do worse than speaking to the 49-year-old.

It will be difficult to hold on to their best players. Ryan Sessegnon draws the most attention and the 17-year-old is raw but has huge potential. Tom Cairney has been more influential, though, and at this stage would be a bigger loss to Fulham. Cairney makes them tick. Half-a-dozen Premier League clubs would like to see the 27-year-old in their colours.

There are massive financial ramifications. A quarter of the entire Championship’s revenue comes from parachute payments. The wealth gap has grown bigger since Fulham were relegated. Khan is empire building in London — his attempt to buy Wembley shows the range of his ambition — and having a Premier League team would be a huge boost towards achieving his objectives.

In Pictures | Shahid Khan: Fulham FC and Jacksonville Jaguars Owner 11 show all In Pictures | Shahid Khan: Fulham FC and Jacksonville Jaguars Owner 1/11 Fulham Chairman Shahid Khan is greeted by fans in 2013 Getty Images 2/11 Getty Images 3/11 Jacksonville Jaguars owner Shahid Khan links arms with players before a Jacksonville Jaguars vs Baltimore Ravens NFL match at Wembley in 2017 Action Images via Reuters 4/11 Fulham Chairman Shahid Khan celebrates after Steve Sidwell scores their team's second goal during a Barclays Premier League match vs Crystal Palace at Selhurst Park in 2013 Getty Images 5/11 Mayor of London Sadiq Khan meets with Shahid Khan, owner of Fulham FC and the Jacksonville Jaguars, at his apartment in Chicago in 2016 PA 6/11 A Fulham fan meets Shahid Khan in 2013 PA 7/11 Shahid Khan holds his personalised Fulham FC Team shirt in 2013 Reuters 8/11 Shahid Khan at Craven Cottage in 2016 PA 9/11 Fulham's Owner and Chairman Shahid Khan applauds in the stands with Fulham CEO Alistair Mackintosh in 2014 PA 10/11 Fulham's chairman Shahid Khan celebrates following his team's 4-1 victory during the Barclays Premier League match between Crystal Palace and Fulham at Selhurst Park in 2013 Getty Images 11/11 Shahid Khan of the Jacksonville Jaguars walks on the sidelines during pregame against the Arizona Cardinals at University of Phoenix Stadium in 2017 Getty Images 1/11 Fulham Chairman Shahid Khan is greeted by fans in 2013 Getty Images 2/11 Getty Images 3/11 Jacksonville Jaguars owner Shahid Khan links arms with players before a Jacksonville Jaguars vs Baltimore Ravens NFL match at Wembley in 2017 Action Images via Reuters 4/11 Fulham Chairman Shahid Khan celebrates after Steve Sidwell scores their team's second goal during a Barclays Premier League match vs Crystal Palace at Selhurst Park in 2013 Getty Images 5/11 Mayor of London Sadiq Khan meets with Shahid Khan, owner of Fulham FC and the Jacksonville Jaguars, at his apartment in Chicago in 2016 PA 6/11 A Fulham fan meets Shahid Khan in 2013 PA 7/11 Shahid Khan holds his personalised Fulham FC Team shirt in 2013 Reuters 8/11 Shahid Khan at Craven Cottage in 2016 PA 9/11 Fulham's Owner and Chairman Shahid Khan applauds in the stands with Fulham CEO Alistair Mackintosh in 2014 PA 10/11 Fulham's chairman Shahid Khan celebrates following his team's 4-1 victory during the Barclays Premier League match between Crystal Palace and Fulham at Selhurst Park in 2013 Getty Images 11/11 Shahid Khan of the Jacksonville Jaguars walks on the sidelines during pregame against the Arizona Cardinals at University of Phoenix Stadium in 2017 Getty Images

Fulham have the class to see off Derby — and either Aston Villa or Middlesbrough in the final — but they can be outmuscled. They are less physical than their rivals and vulnerable in the air. Derby are likely to sit deep again.

If Sheyi Ojo returns from injury, the Liverpool loanee could make a big difference. Ojo’s pace gives Cairney more options and would mean Derby could not pay so much attention to Sessegnon. Fulham are good but if they stumble it may be a while before they can reach this standard again. This is an opportunity they cannot let pass.