Northampton Saints centre Rob Horne has been forced to retire after suffering nerve damage to his right arm.
The injury occurred during the Saints' 27-21 win over Leicester Tigers when he ran into number eight Sione Kalamafoni at the kick-off last Saturday.
Horne, 28, was carried off on a stretcher following six minutes of treatment, having been knocked out and after undergoing tests, neurological consultants confirmed that the damage was career-ending.
"This is absolutely tragic news, and has been devastating for every member of the squad and staff here," said interim head coach Alan Dickens.
"All our thoughts are of course with Rob and his family at this time.
"Rob is not only a world-class rugby player, but he's an exceptional man. He is a hugely respected and popular member of the dressing room and this will be an enormous loss to Saints - both from a rugby and a personal perspective.
"Even though he had only been here for one season, I am sure he was destined to become a club legend and, like everyone, I am deeply saddened that his career has been prematurely ended in this way."
Horne arrived at Franklin's Gardens last summer after 10 seasons with the Waratahs. The centre won 34 caps for Australia, representing them at two World Cups and against the British & Irish Lions in 2013.