Complex sentence: However, on 17 March 2008, he announced his decision to stop playing football: the 28 year-old had heart problems and the doctors told him he would risk his life if he continued playing.
Split into simpler sentences: However, on 17 March 2008, he announced his decision to stop playing football. The 28 year-old had heart problems and the doctors told him he would risk his life if he continued playing.