Mullin was out of matchday squads for the final three months of last season and did not feature in a league fixture after January.
Having not previously spoken publicly about his first-team exile, Mullin’s emotion was clear as he discussed the situation with mental performance coach Dan Donnachie in front of the cameras.
Having missed the start of the season after back surgery, Mullin said he had not completely recovered when he returned to action.
“I understood I had to wait for an opportunity… but when it came I thought that would be it and it would be a chance to carry on where I left off,” he says in the globally-screened documentary.
“It didn’t transpire that way and I let it get to me to be honest.
“From where I’ve been to then only being allowed to play four games and finding myself being left out of the team, I resented it – and I carried that for weeks because I felt it was unjust.”
Mullin also questioned why Parkinson had stopped “trusting” him on the pitch, but added that he had let go of his resentment and was satisfied he had come through a mentally challenging period.
“I’ve not been able to give best version of myself for many factors,” Mullin added. “But I’ve no doubt that eventually I’ll find myself again.
“Whether it’s here or somewhere else, it’s out of my control. I hope it’s here but you never know.”
Morrell says Mullin’s “emotion is understandable because he’s got such an attachment and done so much for the club”.
“It’s difficult to take for any player to sit there watching, but especially for him after it happened so quickly; from being main man to out of the squad,” he added.
“The hurt is obvious and that resentment could have been affecting his performance. It’s good to hear he’s let it go and hopefully he can give himself that chance.”
