Christian Leali'ifano, who has played 19 tests for Australia and is a co-captain of the ACT Brumbies in Super Rugby, has been diagnosed with leukemia.
The Brumbies issued a short statement Saturday saying "it is with great sadness that we inform fans that Christian Leali'ifano has been diagnosed with leukemia," and that he is in hospital for further treatment.
Brumbies interim chief executive Phil Thomson said it was too early to comment much further.
"At the moment it's just a matter of ensuring Christian receives the best care and support he can at this time," Thomson said. "He is one of the most respected players within this group and this news has come as a huge shock to all of our players, coaches and staff. Everyone knows that Christian is an amazing young man, an important member of this team and of the Canberra community."
New Zealand-born Leali'ifano, a 28-year-old inside center or flyhalf, has scored 124 test points. He missed part of the recent England three-test series due to the birth of his first child.
Australian Rugby Union chief executive Bill Pulver, who is in Rio de Janeiro to watch the Australian sevens teams play at the Olympics, said "our thoughts are firmly with him as he begins his treatment."