Valencia, 25, joined West Ham from Pachuca last summer, having scored all of Ecuador's goals at last summer's World Cup.
With five goals to his name this season, Valencia has impressed, and West Ham are unlikely to let him leave without a fight.
However, if Chelsea were to offer a player in exchange, West Ham may well be more inclined to strike a deal - here are three Blues players who West Ham could be interested in.
Nigerian defender Omeruo has spent the season on loan at Middlesbrough, but it's unclear just how much of a future the 21-year-old has at Stamford Bridge. With Guy Demel out of contract at the end of the season, West Ham may want to bring in another player who can fill both right back and centre back spots - which is just what Omeruo would provide.
John Obi Mikel
Alex Song's loan deal from Barcelona expires this summer, meaning West Ham are likely to be in the market for another midfielder. Mikel has been a bit-part player once again this season, and has many similar attributes to Song - whuich could well interest West Ham. Another Nigerian international, Mikel may want first-team football at this stage of his career.
If Valencia is going, then West Ham will need a forward with pace to take his role in the team. Remy has played second-fiddle to Diego Costa this season, and The Mirror even suggested in January that Chelsea were ready to offer the Frenchman to West Ham in exchange for Valencia. A proven goalscorer with Newcastle, Remy would certainly give West Ham a goalscoring threat to replace Valencia.