Leeds United suffered a shock FA Cup defeat on Sunday afternoon.
Conor Shaughnessy's own goal on 76 minutes and a last-minute winner from Shawn McCoulsky saw the League Two side consign United to a second successive third-round elimination, following last season's shambles at Sutton United.
Gaetano Berardi had given Leeds a ninth-minute lead but victory would have papered over the cracks in a major way and fans of the Elland Road club have slammed the players on Twitter for such an inept performance in Wales.
Whelan is also a big Leeds supporter and claims that it was a "joke" to see a number of Thomas Christiansen's side sharing jokes among themselves after the defeat.
He told BBC Radio Leeds: "I saw a couple of players walking out there and smiling to one another and for me that's disgusting.
"If you want to smile then get on the coach but there shouldn't be any smiling going on after a result and performance like that. It's a joke.
"It angers me when I see people coming out with a smile on their face. Do it behind closed doors because I do not want to see that."
If true, you wonder if some of the Leeds players understand the fury that they evoked after their performance.
Losing to a League Two in the third round of the FA Cup is a big deal and Whelan is right, it's absolutely not a laughing matter.