Jonathan Douglas has been ruled out for a minimum of three months with a knee ligament injury.
The Republic of Ireland international was stretchered off in the closing stages of Leeds' 1-1 draw against Walsall last Saturday, and after having a scan the true extent of the injury has now been revealed.
Douglas has been a regular in Leeds' midfield so far this season, making 16 League One appearances in the club's bid to gain an immediate return to the Championship.
Dennis Wise does have other options available, such as on-loan Radostin Kishishev, Alan Thompson, Jonny Howson and Andrew Hughes, but admits that losing Douglas is a blow.
"We're hoping to have him back before the end of the season. He will see the surgeon on Monday and it all depends on what he says," the manager said.
"It's a real blow for us and for Dougie. He's a strong character and he's been leading well as captain. I've been really pleased with him."