Neil Warnock is unsure how long Paddy Kenny will be sidelined for, but expects Mikele Leigertwood to be out for at least three weeks.
Kenny suffered a groin injury during Sheffield United's 1-0 win over Arsenal, while Leigertwood hurt his ankle in the first half.
Goalkeeper Kenny will definitely miss the New Year's Day game at Middlesbrough and Warnock expects to know more come Tuesday.
"We don't know about Paddy, we will know more on Tuesday," the Blades manager told Sky Sports News.
"He will miss Monday's game, but we will know more when he has had a scan. At the moment it is very sore and with the swelling you can see where the bruising is coming out.
"If you saw the tackle on Mikele you could see his ankle go and I think it's very similar to the last time when it was three or four weeks.
"He will have to have a scan. You can feel very sorry for him, but that's life, it happens in football and you just have to get on."
Phil Jagielka took Kenny's place in goal for the closing half-hour against Arsenal and Warnock explained his philosophy behind not having a recognised substitute keeper.
He added: "I think 95 per cent of the time I have another option with a forward to win a game or get us a point. It is more important to have that option.
"If I was a young manager I wouldn't dare do it - it doesn't make sense when you've got five subs.
"Jags ain't a bad keeper and it just gives me an extra option to win. I try to be very positive with the subs."