But X-rays yesterday revealed no fracture and the 20-year-old Sculthorpe should be available when Saints open their Super League campaign at The Willows on 5 April.
"The leg is bruised and swollen, and it's painful, but I think he should be OK for Salford," Geoff Sutcliffe, St Helens' football manager, said.
There is bleaker news, though, for two of Saints' other casualties - the winger Chris Smith and the prop Apollo Perelini, who were also injured at Odsal. "Chris Smith has an ankle ligament injury. It's badly swollen and he'll be out for perhaps three weeks or so," Sutcliffe said. "Apollo's got damaged knee ligaments and he'll be out for a similar time."
More injury gloom concerns the Saints hooker Keiron Cunningham, who faces two months on the sidelines after aggravating a long-standing groin problem.