The midfielder has had to bide his time since arriving from Swansea, but David Moyes admitted Downes’ performance in Belgium gave him food for thought.
However, Maxwel Cornet, his summer colleague, will miss Fulham’s trip to the London Stadium with a sprained calf.
Ben Johnson made his return from injury in a back three during the week as Moyes took the opportunity to rotate his side, although all of Delan Rice, Lucas Paqueta and Gianluca Scamacca are set to start on Saturday.
“Maxel will not be available for the game,” Moyes said at Friday’s pre-game press conference.
“He has a small calf sprain. I don’t think it’s as bad as we initially feared, but it will keep him away for a few days.
“Elsewhere we’ve had a few knocks and troubles but hopefully we’ll be fine by the time we get to Sunday’s game.”
Predicted West Ham XI (4-2-3-1): Fabiansky; Coufal, Dawson, Zouma, Creswell; Downes, Rice; Bowen, Paqueta, Fornals, Scamacca
injured: Cornet (veal)