The newly-promoted Premier League side called off Wednesday's friendly against Coventry City as a "precautionary measure" after what they described as "a small number of positive Covid-19 test results within City’s first-team group."
The Canaries are due at Bramall Lane on Saturday for what is supposed to be the Blades final friendly before they open their Championship campaign at home to Birmingham City on the evening of August 7. It is also due to be new manager Slavisa Jokanovic's first game at his new home ground.
The Blades have only organised three friendlies this summer.
They suffered two positive tests themselves amongst the squad when on tour in Spain, where they played Gibraltan side Europa Point.
They face League One Doncaster Rovers on Wednesday, July 28.
Support The Yorkshire Post and become a subscriber today. Your subscription will help us to continue to bring quality news to the people of Yorkshire. In return, you'll see fewer ads on site, get free access to our app and receive exclusive members-only offers. Click HERE to subscribe.