Ravenhill, 31, was one of Bradford's top performers during the second-half of last season after arriving on a free transfer from Notts County.
However, after being sidelined for three months by a knee injury sustained in pre-season, he has found it difficult to force his way back into Parkinson's starting line-up.
"Ricky is frustrated, he's done really well to get back from his injury. He came to see me the other day and he's determined to play," said the Bantams boss.
"But by the end of this season Ricky will have played a massive part. You have to bear in mind, before he got injured he was the key player in the team in pre-season and was set to continue.
"But when you get injured there is always somebody else there to come in and grab that shirt and that's what Nathan Doyle and Gary Jones have done, but Ricky is more than good enough to come into the team and hold his own."