The Hammers swooped for the Ecuador international after he netted three times during the group stages of the 2014 World Cup, but he’s struggled to transition that scoring prowess to the Premier League.
Although injuries have been a factor, the 26-year-old has scored just eight goals during the last two Premier League campaigns – including four in 15 appearances last season.
According to The Daily Mail, the East London club have already received an offer from Lazio – a year-long loan with a guaranteed permanent £10million transfer next summer.
But Slaven Bilic’s side want to recoup £12million for Valencia, the exact fee they paid former employers Pachuca two summers ago.
Furthermore, West Ham are keen to sign a direct replacement before selling the 29-cap international.