Matthew Mann talks to the former Newport County defender about his incredible rollercoaster ride

MARK O’Brien had the world at his feet. The Irish defender became one of the youngest players to represent Derby County, making his debut aged 16 in a Championship match against Watford in May 2009.
When he returned to Pride Park ahead of the 2009-10 season, he had reason to be optimistic. But a routine check during pre-season identified a serious problem with his heart. It was one that would have life-changing consequences.
“We wore heart rate monitors during training,” O’Brien says. “During ...