The FA Cup finalists are putting on a charity game in his honour as they aim to raise even more money for his recovery.
McCall was diagnosed with Ewing's Sarcoma, an aggressive form of cancer, aged just 23.
The recent news rocked Hemel, who have gone into overdrive after he was told the news having first thought he had broken his leg after feeling severe pain.
Former Hornets stars Lloyd Doyley, Will Hoskins and Darren Ward take to the field at Vicarage Road as they raise cash for three cancer charities.
The Tudors have already helped to raise £10,000 for his recovery - and were able to hand over a cheque for more than £3,000 as fans opened their wallets on Bank Holiday Monday with a legends’ game at Vauxhall Road.
Hemel, with the player and his family’s permission, detailed the 24-year-old’s off field battles after his sudden diagnosis earlier this season.
“Many of you will know that Spencer has struggled with injury since the end of last season,” a statement read earlier this year.
“With no sign of the injury clearing up Spencer has spent a lot of time at the doctors and hospital trying to determine exactly what the problem is.
“Initially Spencer was told that he had a fracture in his lower leg, however a few weeks ago Spencer was diagnosed with Ewing's Sarcoma, which is a rare type of bone cancer and he is currently undergoing a course of chemotherapy.
“Spencer is 24 years old and has been with the club since signing from Wingate & Finchley in October 2017.
“In that time it is blatantly obvious to anyone that has met Spencer what a great lad he is. Spencer is tackling this with the same determination he shows on the football pitch, head on and with everything he has got.
“All of our thoughts and best wishes go out to Spencer and his family at this time, we look forward to seeing him back at Vauxhall Road in better health soon.”