Brough has made just seven appearances this season due to injury
Darlington midfielder Michael Brough will miss the remainder of the season in order to undergo surgery on a recurring knee problem.
Injury has restricted the 29-year-old to just seven appearances this season, having joined the club on a one-year deal during the summer.
"It's the same knee problem as [Gareth] Waite," Cooper told the club website.
"He's been carrying it a while and we've just been managing the injury and we knew this might happen."
Cooper added: "He'll likely need an operation. He's going to see the doctor this week but the physio has looked at it and thinks he'll need the op.
"It's a big loss. When we got him back in the side the results improved."
The experienced midfielder joined Darlington following his release by Mansfield Town at the end of last season, and lists Notts County, Stevenage and Forest Green Rovers among his former clubs.
Meanwhile Cooper is keen to expand the squad at the Arena, as well as persuade Carlisle United midfielder Marc Bridge-Wilkinson to remain part of the squad.
"We're not kidding ourselves, we do need to be better," Cooper told BBC Tees.
"We need to bring better players into the football club to make the group that we've got even better, and that's what we're trying to do as we speak.
"We're halfway through the league season, the table doesn't lie, which suggests we're not quite good enough at the moment compared to where we want to be.
"We've got to do whatever we can do to make it better and part of my job as a manager is to make it better and bring in reinforcements."
Bookmark with:
What are these?