The 24-year-old was forced to withdraw from the Toffees’ 4-1 FA Cup fourth round win over Brentford on Saturday afternoon in Frank Lampard’s first game in charge.
There were further concerns over the severity of his injury when the former Norwich City man was spotted leaving Goodison Park on crutches.
Lampard confirmed after the game that Godfrey’s injury isn’t “not good” and is facing a lengthy spell on the sidelines.
Ben Godfrey joins Everton injury list
“It’s a hamstring injury, which is to be assessed,” Lampard confirmed.
“It’s not good, he will be missing for a period of time. I don’t necessarily know the severity of the injury but it’s a hamstring.”
Godfrey will join midfielders Tom Davies, Abdoulaye Doucoure and Fabian Delph in the treatment room.
Neither of the four players will be fit for the visit to St James’ Park, though Everton could hand debuts to January signings Donny van de Beek and Dele Alli.
Dominic Calvert-Lewin could return
Lampard is also hopeful striker Dominic Calvert-Lewin will be in contention after returning to training on Friday.
The England international has been suffering with a knee injury,
“I’m hopeful,” Lampard said when asked if Calvert-Lewin would return against United.
“He was training outside yesterday on his own so hopefully he will be in the team tomorrow.
“Whether he is ready in three days’ time is one of those. We will have to see where he is at in terms of being game ready.
“I’ll probably know more about that in the build-up to the game in the next couple of days.”
Eddie Howe side’s will go one point behind Everton if they win at St James’ Park.