Speaking to ESPN Soccernet, Whelan said: "I've no idea why Johnson said no, I think he didn't fancy coming north. It would have been a good deal for us, but that's football."
The DW Fitness owner also revealed that he expects Tottenham to be the favourites to land Rodallega, ironically on the same day as the Latics travel to White Hart Lane for tonight's fixture.
Whelan added: "We are used to Tottenham making a last minute bid on transfer deadline day, and by last minute, I mean the very last minute.
"I have seen Spurs linked with Rodallega for some time, but we have not received a bid, not even an enquiry as far as I know. But that doesn't mean they won't make a bid, but if they do they always leave it late, very late."