All trains will be cancelled between Brighton and Haywards Heath between 12.30am and 9am for emergency engineering work.
The disruption could affect football fans setting off early to travel to Leeds for Brighton and Hove Albion’s final away game of the season.
Train operator Southern said: “Colleagues over at Network Rail have discovered an urgent defect to a set of points that needs repairing.
“It’s better to do this sooner rather than later and, although there’s never really a perfect time to close the line, fewer people use the network during the night.
“Generally, trains will run non-stop between Brighton and Haywards Heath in both directions via an alternative line which is via Lewes.
“If you’re travelling between these times, please check National Rail Enquiries Journey Planner to see if your train is affected.
“Your trip will take longer than usual and you may have to use a replacement bus service for a portion of your journey.
“The odd train via Littlehampton may also be affected. It’s important to check online on Saturday, as you might need to complete your trip earlier than expected.
“Staff are liaising with suppliers to source rail replacement buses to run between Brighton and Haywards Heath.
“Ones which have been confirmed have been advertised in journey planners.
“We will continue to update journey planners as and when the supplier confirms.”
Southern also said: “Engineering works are taking place between Haywards Heath and Brighton from 12.30am on Sunday morning.
“As a result of this, trains may be cancelled or revised between these stations.
“This is expected until 9am on Sunday 15 May.
“From approximately 12.30am until 9am on Sunday morning, Southern and Thameslink services to and from Brighton will run differently than usual.”
Southern said that there would be no service at Preston Park, Hassocks, Burgess Hill and Wivelsfield stations.
