The likes of Keiren Westwood and Sam Hutchinson have had little or no game time under manager Jos Luhukay this season.
Goalkeeper Westwood has never featured under the Dutchman, who arrived at Wednesday almost 12 months ago.
Coach Bullen, who deputised for Luhukay during the press conference ahead of Saturday's visit of Preston North End, says the players have not downed tools despite them being out of favour.
"They have been totally professional," said the Scot.
"Obviously they are disappointed because they want to take part, they want to be involved - especially when you see your teammates going through a hard time results-wise.
"I'd be the same.
"But they've been nothing but professional and have come in every day, training as best they can whether that be with the first team or the under-23s.
"They've been spot on.
"Every single one of them has been fantastic."
Last week saw David Jones re-enter the first team picture when he was named on the bench for the defeat at Swansea.
And Bullen says there is always the prospect that the likes of Hutchinson and Westwood could come back into the manager's thinking.
"You can never say never," he added.
"It was mentioned at the fans' forum that the manager makes the final decision and that's the way it should be.
"He has made that decision up to now and if he feels it's right to bring them back into the fold then he'll make that decision."