The South American striker jetted to London over the weekend for talks ahead of a likely £12m move from Mexican side Pachuca.
Valencia was one of the top performers of his nation’s showing in Brazil, netting three goals in three games as La Tricolor slipped out at the group stage.
Prior to the competition the winger converted to centre-forward was impressive in Liga MX, firing 12 efforts as his side reached the Clausura play-off – which they lost 2-0 to Leon.
West Ham have since stepped up their interest, with Sam Allardyce desperate to bring a more attractive playing style to Upton Park.
Downing says that Valencia will be an exciting option for the Hammers, and will give them an alternative option to main front-man Andy Carroll:
“We can’t rely on Andy all season,” he is quoted by Goal.
“He was the big signing last season, but Andy struggled with injuries so hopefully the new signings will take the pressure off him a little bit.
“And from what I’ve seen of Valencia against England, he looks a very good player.
“He can nick a goal and it is competition for places. It’s what we’ve needed as we didn’t have that last season.”