Casley penned a note to his team-mates informing them that his body was no longer ‘up to the standard of international softball anymore’.
Casley played through the pain barrier at the world championships at Albany earlier this year to lead New Zealand to a triumph.
His three-run homer in the middle of the game assured New Zealand of the 4-1 victory over Venezuala in the final.
Casley said that after four bouts of surgery on his knees, a fractured vertebrae and on-going shoulder injuries he couldn’t realistically ask players to prepare by doing things that he was no longer able to do.
“This is not something I have taken lightly. The Black Sox have been the biggest part of my life for 14 years. My heart is still very much with the team, but my body is telling me enough,” he said.
Casley said informing new Black Sox coach Mark Sorenson of his decision was one of the hardest things he had ever done.
However, he said the memories of leading the team, and the friendships made would be something he would cherish forever.
Casley said he would not be lost to the sport as there were important issues in the future that needed to be worked on with new administration moving into the sport.
New Black Sox coach Sorenson said Casley’s loss was a blow to the team.
“Rhys is a strong leader and was an integral part of our plan of having continuity in leadership.
“It’s a shame because he still had a lot to offer the game,” he said.
Sorenson was given Casley’s news the day before a planning meeting for the side ahead of the defence of their world title in two year’s time.
“He knew we were having the meeting and wanted to let us know beforehand. But we’ve got two years to work around a new captain. I will also consult Eddie Kohlhase, who was coach before me,” Sorenson said.
Kohlhase said Casley had been one of the world’s best hitters and a fine gloveman.
“We appointed him in 2010 to lead the campaign for this year’s world championships and he just grew into the role and turned out to be a fantastic leader.
“He shouldn’t have played in the tournament. We were trying to facilitate him in some way but he couldn’t throw a ball.
“He had broken his shoulder and had an operation to re-attach muscle to the bone and it hadn’t healed. We always planned to use him in a batting capacity. There was no danger of him damaging his shoulder further but I understand he needs another operation,” he said.
His feat in hitting the winning home run which scored three runners and broke the final open summed up the value in his career, Kohlhase said.