The Ecuador international has shot to fame since joining the JJB Stadium outfit - initially on loan - in 2006, making 84 league appearances for the Latics, netting seven times.
The former Villarreal forward has long been linked with a summer move to either Manchester United or Real Madrid, with Sir Alex Ferguson's side now the favourites following Real's £80 million acquisition of Cristiano Ronaldo.
However, Athletic chief Whelan has now revealed that a new club have expressed an interest in the 23-year-old.
"We don't want to sell him, it's the big clubs that are chasing him that are offering fantastic money for the lad and I don't want to stop a player with his ability from playing with one of the top six clubs in the world," he told Sky Sports.
"I don't want to sell him, but if Antonio Valencia goes, which he could do in the next fortnight, it creates a problem on the right for us because he's going to be so difficult to replace.
"We have got three clubs vying to buy him. We are just going to sit on the fence because, whatever we think, it depends on where the player wants to go.
"There is no use us thinking we will sell him to Real Madrid or Manchester United, because it depends on the player and the advice his agent gives him.
"If he wants to stay, though, I'm delighted. If nothing happens and he stays I will be over the moon, and the supporters will be."
Liverpool are now being linked with Valencia, with Rafael Benitez expected to spend heavily on replacements during the close-season in order to finally secure a first Premier League title for the Anfield outfit.
The Reds are reportedly closing in on the signature of Portsmouth attacking right-back Glen Johnson for around £18 million.
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