"Ricky Ravenhill has expressed his desire to go out on loan," Parkinson said after Sunday's home defeat to Tranmere.
"He feels he's at an age where he needs to be playing regularly and I agree with him."
Parkinson brought in the versatile Matthew Bates last week as cover for injured centre-half Andrew Davies, who will be sidelined for four months following knee surgery, and also for Ravenhill should he find a new club.
On Bates' arrival, Parkinson added: "It's three-fold really. Obviously with Andrew getting his injury, he can help us in central defence.
"Matty can also play full-back and he can play in midfield as well.
"I feel it is time for Ricky to move on and get some football, so Matt covers us in midfield in Ricky's place.
"He covers us at right-back as well, along with his favourite position of centre-back."
Bates was an unused substitute against Tranmere on Sunday, while Ravenhill has made a total of 64 first-team appearances for City since joining on a free transfer from Notts County after an initial loan spell in January 2012.