Manager Chris Wilder will speak to his Sheffield United players after revealing a number of them played through illness during Tuesday night's Carabao Cup tie against Hull City.
Mark Duffy, and at least two other unnamed players, suffered with a virus ahead of the penalty shoot-out defeat to Nigel Adkins' Hull and will be assessed by medical staff before Saturday's Champonship clash against Norwich City.
Duffy was taken off at half-time against Hull after feeling 'light-headed' and the ill players were absent from United's Shirecliffe training base yesterday.
And Wilder said: "Duff was in a bit of a bad way on Tuesday and then a couple more went down with a virus. A couple struggled through.
"I'll have a chat with them because they played and maybe they shouldn't have. There's an honesty in terms of wanting to get out there and put in a performance, but it maybe stepped over the line of being sensible.
"We're hoping it'll quickly clear up and they train before the weekend. On one hand I'm frustrated that they didn't flag up to me how they were feeling, but I can also look at it philosophically, that I have a group who all want to play.
"Duff didn't know much about the first-half against Hull, which was just as well because he had a nightmare, and hopefully he and the others can train ahead of the weekend."
Wilder, who hopes to sign another player before his side take on Daniel Farke's men, added: "It's a difficult one for the players. Fans will always judge them on their performances and they want to play, put themselves in the managers' thoughts, but on the flipside they can't play to the best of their ability if they're not 100 per cent.
"As I say it's a touch disappointing that I didn't find out about it until after the game but it's not a major criticism. At least I haven't got boys who are fit and don't want to play for the club... you're bang in trouble when players who are fit take an extra week or two off.
"We haven't got off to the best of starts in terms of the first two results, but that's when you need players to say 'I'm ready and prepared to do a job to get us up and running'."
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