That's according to Football Insider, who suggest that the Whites are eager to get the former Real Madrid man off the books to free up space on their wage bill.
The report states that Casilla is on around £40,000-a-week, and that Leeds are aware that they will struggle to engineer a deal for him at that price.
As such, they could look to cut their losses and let him leave Elland Road for nothing, with view to bringing in another stopper to act as Illan Meslier’s understudy.
The young Frenchman has cemented his spot as first choice between the sticks in Yorkshire, and has featured in all but one of Leeds' Premier League matches so far this season.
Casilla has managed just three outings in all competitions this term, conceding five goals in the process from an xCG (expected goals conceded) of 4.71.
Elsewhere, Bradford City manager Mark Trueman has opened the door for Leeds youngster Bryce Hosannah to return to the club on loan this summer.
The 21-year-old has spent time with the Bantams before, but had his previous spell cut short by injury.
Speaking to the Telegraph & Argus, Trueman said: “We want to bring the best players possible to the club, whether that’s loans or signings in the summer window.
“If Bryce is a player that is available, there is always potential that he could return.”
We’ve gathered the rest of today’s Premier League transfer rumours below: