Derry are planning without midfielder PJ McCloskey for Saturday's all-Ulster clash with Cavan in the All-Ireland SFC qualifiers.
It has been revealed that McCloskey suffered cruciate knee ligament damage during the Oak Leafers' second round win over Down earlier this month.
The Banagher clubman requires surgery and will play no further part in Derry's Championship campaign which they hope to extend when entertaining provincial rivals Cavan at Celtic Park on Saturday (throw-in 7pm).
Derry manager Brian McIver told the Irish News: "It's obviously a loss for us, especially given the performance PJ put in the last day against Down. It was probably one of the finest midfield displays of 2013 so far."
McCloskey was in man-of-the-match form against Down in what was only his second Championship start. He won eight kick-outs and dovetailed superbly with Patsy Bradley as they dominated centre-field.
This latest injury is a cruel blow for the 27-year-old who missed the 2011 and 2012 Championships through injury. A hip problem also kept him out of Derry's Ulster SFC quarter-final defeat to Down last month.
Teenage forward Ryan Bell, who shot 0-6 against the Mourne men last time out, could revert back to midfield where he played earlier in the Championship, while Barry McGoldrick, Bliain Gormley and Ryan Dougan are also options in that area.