Siddal Masters were playing away at Ossett Trinity Masters when, just three minutes into the game, an Ossett player collapsed.
With players rushing to his aid, it was Siddal player, Mark Warrender, who took control.
Mark, a firefighter for 27 years, said: "It was only about three minutes into the game and he just collapsed.
"He was face down and wasn't moving - usually if someone goes down there's some sort of movement, but he was just still.
"One of the Ossett players ran over and I think it was their manager who ran on and put him on his side.
"We thought he had had a fit to begin with, but when he was moved onto his back, we realised he wasn't breathing."
Luckily, a life-saving defibrillator at the club was brought to the pitch while worried bystanders called emergency services.
"CPR was started while someone went for the defib from the club - time was critical," Mark said. "The quicker the defib gets to them the better."
Following the instructions given by the defibrillator machine, CPR continued to be given.
Mark, who is playing his third season with Siddal, said: "It tells you what to do, continue CPR, then to stand back while the machine analyses the patient. You have to let the machine do its work.
"Then it said to shock him."
More CPR was given and Mark said the man seemed to come around a little bit and was trying to breathe.
"We continued to do what the defib said. two Ossett players were doing the compressions, then the defib said it was analysing again and instructed another shock."
It was then the man started coming around.
"He lifted his knee up and there was movement. He started talking a little bit and was breathing. The paramedics arrived and Yorkshire Air Ambulance landed."
The man was taken by the ambulance to Leeds General Infirmary, where it's believed he is in a stable condition.
Mark said: "If there was a time for something like that to happen to him then that was it. There were people who knew what they were doing there to help. If he'd have been alone, just out for a walk, it could have been a different story."
Mark said everyone pulled together from the players to a bystander who was a first aider.
"There were people there who had training and knew what they were doing.
"When something like that happens, you're waiting for medical care to turn up, so it's so important for clubs to have defibs and for them to provide courses for coaches, and players, on how to use them so the help is there in cases like this."
And it's not the first time Mark's heroics have saved a life out of uniform.
"I've used defibs at work and once before in civvy street at a swimming pool in Sowerby Bridge. A young man, only in his late teens, early 20s, collapsed while swimming. I saw what happened and there was a defib on site. His life was saved.
"They are a very useful piece of equipment that save lives."
Ossett Trinity Masters manager, Jeff Chappell, who is a former firefighter, was also playing on the day and said he has since spoken to his fellow player who is still in hospital.
"He's having all the tests, but it's hoped he'll be home soon enough.
"The paramedics and ambulance workers did a fantastic job, they were there within minutes and Yorkshire Air Ambulance arrived a short time afterwards.
"There were ex-firemen involved in it all - first aiders...everyone pulled together.
"Mark took the lead and organised everyone - someone needed to take charge otherwise it would have been chaos.
"It was a fantastic team effort, the players, the people ringing the ambulance, those running for the defib, everyone played a part.
"At Masters, we make sure everyone is ok. We look out for one another and everyone who was involved played a part. So a massive thank you to everyone."
Jason Greenwood-Macdonald from Siddal ARLFC said: "Siddal as a community based club are so grateful to all our volunteers.
"Having people like Mark gives us great confidence that our members are in good hands. We are hoping what Mark did yesterday will encourage others to learn how to resuscitate and use a defibrillator."
Mark added: "I'm so pleased he seems to be doing OK and I hope he makes the best recovery he can.
"Rugby league is an exceptional family to have. There's nothing else like it."