England and Nottinghamshire batsman James Taylor has been forced to retire because of a serious heart condition.
Scans have shown that Taylor, 26, has a condition similar to the one which affected footballer Fabrice Muamba.
Taylor, who has played seven Tests and 27 one-day internationals for his country, posted on social media: "Safe to say this has been the toughest week of my life!
"My world is upside down. But I'm here to stay and I'm battling on!"
Taylor felt ill during the first day of his county's pre-season fixture against Cambridge MCCU last week and was taken to hospital.
It was initially thought he had a viral condition, but he has since been diagnosed with Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC) and needs an operation.
Taylor later posted on Facebook: "Absolutely overwhelmed with all the support I've received. You don't understand how much it means to me and how much it helps! Thank you!"
England team director Andrew Strauss spoke about his "shock" and "sadness" at the news.
"Throughout his career, he has constantly impressed with his determination to make the absolute most of his ability," said Strauss.
"It is immensely cruel that such a hard-working player will be unable to fulfil his great potential in the international arena."
Footballer Muamba collapsed when his heart stopped for 78 minutes while playing for Bolton Wanderers against Tottenham Hotspur in 2012.