Sheffield United have sacked manager David Weir and his assistant Lee Carsley, the club have confirmed on their official website.
Chief executive Julian Winter said: "First and foremost all at SUFC, from the board right the way through the club, wish David and Lee all the best for the future. None of us wanted to be in this position at this point in the season. David's appointment was made as part of developing a new phase at the club.
"Chris Morgan has been asked and agreed to take an interim role in charge of Sunday's team. He knows the players and, with Darren and Travis, will be doing his upmost to get a return to winning ways," added Mr Winter.
Chris Morgan said: "The club have made me aware of the situation and I am happy to step in and work with the players for the Coventry game."
Sheffield United are currently 22nd in League One.