Bradford defender Andrew Davies has been ruled out for up to four months after undergoing knee surgery, it has been confirmed.
Davies, 27, hurt his knee in the recent defeat at Burton, the same game in which fellow centre-half Luke Oliver sustained a season-ending Achilles injury.
"Andrew had his operation on Friday and he'll be out for three to four months as we thought," Parkinson said after his side's FA Cup draw at Northampton at the weekend.
"It's obviously a big blow to us because Davo's a big character for us.
"It wasn't really until we got back on the coach on Tuesday night (after the Capital One Cup win at Wigan) that we got confirmation that Andrew's injury was as bad as it is. The surgeon wasn't 100% about the injury until that point."
Parkinson has moved quickly to draft in cover for his injured central defenders, with Republic of Ireland Under-21s international John Egan, 20, joining on loan from Sunderland until the new year.