Halfpenny is not the only Wales full-back who has been training at Cardiff with Liam Williams, 34, also taking part in sessions at the Arms Park while he tries to prolong his career by recovering from his latest knee injury.
Cardiff do have back three concerns with Wales wing Mason Grady suffering another injury, after only just returning from a 10-month lay-off because of a knee problem.
This time Grady, 23, damaged his shoulder in his comeback match as Cardiff hammered Richmond 71-10.
“It’s a shoulder injury, but we’ll have to assess it in the next 24-48 hours,” said Sherratt.
“Fingers crossed it’s ok because Mason deserves a bit of luck. He’s had a tough 18 months so let’s hope that he’s ok.
“You learn in this game that until you have a good look at it, you don’t know.
“I’m hoping that it’s not as bad as it looks and we get a scan that is low grade. Until we have a look at it, I don’t want to get too downbeat.”
Cardiff have another pre-season game against Leinster before opening the United Rugby Championship (URC) campaign at home to South Africa side Lions on Saturday, 27 September.
