Influential midfielder Fergal Doherty will be unavailable for Derry's All-Ireland SFC second round qualifier against Westmeath on Saturday evening.
Doherty is facing a lengthy lay-off, following scan results on the shoulder injury he picked up as a second half substitute in the first round win over Carlow.
Speaking to the Irish News, Derry manager Damien Cassidy said: "Fergal will be out of action for six weeks at least.
"He was due to have a scan today (yesterday). We are hoping he would not need an operation."
Doherty's midfield colleague Patsy Bradley is facing a race against time to prove his fitness. He missed the Carlow game with a back injury.
"We will see how Patsy goes this week, but he is back in training," explained Cassidy.
"We won't be making a call until Thursday. It would be great if he was able to give us something on Saturday, so that's a positive given what has happened with Fergal."
All-Star forward Paddy Bradley is not expected to feature against Westmeath in Mullingar. He failed to make the starting line-up to face Carlow and decided to walk away from the panel, leaving his inter-county career in some doubt.
Bradley said recently that he plans to retire from top level football at the end of the current campaign, but it now looks like the Ulster SFC preliminary round loss to Armagh in mid-May could be his last game in Oak Leaf colours.
His brother, Eoin, top-scored with 1-6 against Carlow and would dearly love to see his sibling return before Derry's Championship run comes to an end.
In a recent interview, Eoin said: "Hopefully he comes back for the next day. I don't live with him so I don't really know what he's thinking, but I think something can be done.
"He is probably one of the best forwards in Ireland over the last 10 years. It's not really something I should be commenting on and Damien will sort something out.
"He texted me after the Carlow game to say 'well done', so his heart is still in Derry football."
Cassidy also confirmed that corner back Kevin McGuckin has not left the Derry panel. McGuckin missed the qualifier clash with Carlow due to the birth of his child.