Newly promoted Premier League side Fulham have made offers for four centre-backs this week.
The Craven Cottage club are determined to secure defenders to avoid relegation at the first time of asking.
Manager Marco Silva is aware his side is not strong enough at present for the top flight.
According to Sky Sports, Fulham want West Ham United's Issa Diop and Chelsea's Malang Sarr.
They are also pushing to secure Arsenal shot stopper Bernd Leno, either on loan or permanently.
Fulham have not stayed up in the Premier League since the 2012-2013 season.
