"There's been no official bids yet, and I think it'll be another week to 10 days before things get as serious as that," Whelan told the Wigan Observer.
"But let me tell you, he's worth a hell of a lot more than the fee we're asking.
"Whichever club gets Charles will be getting a great player for far less than what he is actually worth.
"The problem is, he got a bit damaged by what happened with Birmingham last summer.
"Clubs are perhaps looking at him and thinking twice, thinking he's difficult, but that wasn't his fault at all.
"It was the agents who were to blame for what happened, not Charles."