Defender out for weeksSean Morrison will be out for several weeks with a knee injury.
The defender picked up the problem in training leading up to the Blackburn game, having played every minute in the Sky Bet Championship so far this season.
Manager Nigel Adkins said after the game, "He unfortunately has a knee injury so will join Wayne Bridge in being out for a while, several weeks on the sidelines. It's a blow because he was doing really well.
"But Kaspars and Pearcey kept a clean sheet, we've got Chris Baird who played centre half for Northern Ireland last week and Chris Gunter who has done the same for Wales.
"That's when you look to your squad, Stephen Kelly has also played there and we brought young Niall Keown with us today. He's been training with the first team this week, as Pierce Sweeney did last week. It's why you have a squad, it's a situation we'll have to address if and when it arises."
The boss was asked about Royston Drenthe, confirming he picked up a knock in training, saying, "He trained really well last week, picked up an injury on Tuesday so that ruled him out today."
Shaun Cummings missed the game with a minor injury, joining Bridge, Drenthe, Morrison, Karacan, Leigertwood and Roberts on the sidelines.
Adkins has an exceptional group of forward players, with the likes of Billy Sharp and Jobi McAnuff biding their time to get on the pitch.
The boss simply cannot play everyone, saying, "We've got an extremely strong group of players from a forward point of view.
"Today Hal was going to start, we knew he would be important coming into the midfield area and clearly in the first half you could see we didn't have enough of the ball in midfield. So we changed it and were more dominant.
"If I play Billy, Alfie, Pav, Garath, Jordan, whoever, it doesn't matter if we don't have a grip of the ball. I can't play everyone!"