Kell's leg was broken in December, as United beat local rivals Hull City 2-1, following a reckless and late challenge from Mike Edwards.
Both his tibia and fibia were displaced.
"The surgeon has told us it will be September before Richard is ready to play again," Brian Laws told the Scunthorpe Evening Telegraph today.
"He is definitely ruled out of our plans for the start of the season.
"Obviously that is a blow to us, especially when we will be operating with a smaller squad.
"Richard is making progress and one thing I do know is that he is working his socks off to get back."
Club physiotherapist Nigel Adkins also confirmed this when he spoke exclusively to Iron-Bru.net
"He's in every day and he works ever so hard, he's seeing this as an opportunity to improve his physical body," he told us.
United will also be without record signing Steve Torpey, who will sit out through suspension after being sent off for stamping in the goaless draw at Leyton Orient.