Ben Young is also missing with a fractured wrist, but Perkins remains confident.
He said: “We’re down on troops, but we’re playing at home and I was encouraged by how we went against Hunslet. We’ve just got to stay in the battle this week.”
On York, Perkins added: “They’re a good team and where they’re sitting on the table proves that.
“Their outside backs are important to them; they get in and take some early carries, so we’ve got to combat that and slow down those first few plays.”
Thornton said: “We were poor the last time we played Hemel, but we’ve improved since then.
“However, they will have also improved. They’ve had more time together and played together more often. We know this will be a difficult test.”