Lucas Perez is close to leaving West Ham for Real Betis but an offer for Javier Hernandez from Valencia has been rejected.
Former Arsenal forward Perez is set to leave for £3.5m, having failed to make an impact in east London.
It comes as the Hammers look to tie up a deal to sign Maxi Gomez from Celta Vigo.
Hernandez, though, looks set to stay with the Hammers after Valencia had a bid, believed to be in the region of £7m, turned down.
West Ham boss Manuel Pellegrini is willing to let Perez move on despite fears that striker Marko Arnautovic faces a lengthy spell on the sidelines.
Arnautovic, who signed a new deal on Saturday after interest from China, limped off midway through the second half of the defeat at Wolves following a tackle from Ruben Neves.
He left Molineux on crutches with a protective boot on his right foot.
Pellegrini said: “It will not be an easy injury. I hope he hasn’t any problems but we must review him with an examination.
“It was a hard kick in his foot. I’m disappointed about that and disappointed because we have just 15 fit players.
“We don’t have any creative midfielders in this moment so it’s difficult playing so many games with the same 15 players.”