Hardaker signed for Rhinos at the start of the week and was named in the initial 21-man squad for the game.
"Thankfully, due to the quick actions of a paramedic who lived on the street where he had collapsed, Hardaker was taken to Pinderfields hospital where he had various investigations before being safely discharged home.
In the statement, Rhinos chief executive Gary Hetherington said: "At this moment in time our only concern is Zak’s health and we will provide to him and his family with whatever support is required.
“The Rhinos medical staff are overseeing things and will be arranging a series of medical tests which will then give a clearer prognosis for his recovery.”
Hardaker, 30, had trained with his new team mates on Tuesday morning before a community team activity after lunch.
He said: “Firstly, I would like to say a huge thank you to the paramedic who came to my aid and administered first aid before the ambulance arrived.
"It does not bear to think about what might have been the outcome without her quick thinking.
"It is so disappointing that I will not get to play on Friday, but the Rhinos have given me great support and I will make sure I complete all the tests necessary and I hope to be back on the field as soon as possible.”