The on-loan Blackburn frontman has scored just once since returning to Tannadice in the summer and was dropped for last week's 4-2 win over Ross County.
But midfielder Rankin believes the Scotland international - who made just six starts at Ewood Park after his £2million move south - is trying too hard to impress the Tangerine support that grew to idolise him in his first goal-laden spell with the club.
"Goodie will work hard no matter what," Rankin told Press Association Sport. "He knows himself what he needs to do to get back in the team and I don't see him dropping his standards.
"When he was dropped last Sunday, he was the first to wish the lads luck and the sort of person Goodie is, he will just roll his sleeves up and work to get back in the side.
"I don't think he has got a confidence issue. It is always hard when you have not played games for so long to come back and try to find your sharpness. But we see in training every day how good he is.
"I don't honestly know what is going on with him but I'd like to see him back to the Goodie of old. Maybe he's trying a bit too hard. When that happens it doesn't come off for you. That's something that's good though. It shows he's not willing to accept how things are. Maybe if he just relaxes a bit things will comer easier to him.
"Form is temporary and class if forever. Goodie has certainly got a bit of class about him. He'll be back."