Toulon full-back James O'Connor has reportedly been hospitalised after falling ill on the team bus following last week's win at Oyonnax.
It was reported in the French media that the international suffered a suspected heart attack, but that has been talked down by the club.
"James O'Connor felt unwell in the bus taking the team back from the Oyonnax game (last Sunday)," coach Bernard Laporte told RMC radio.
"The medical staff decided to take him to hospital and he underwent a considerable series of tests."
He added: "I can reassure everyone he's fine."
"He will play rugby again but he will undergo further tests next week.
"James will miss three weeks, maybe four weeks of competition."
O'Connor is currently in his second spell with European champions and has amassed 44 caps for Australia since making his debut in 2008.
Late on Friday, the versatile back posted a message on social media, allaying fears about his health.
No heart attack..
Hypoglycemia & game/training fatigue
All tests were very positive%uD83D%uDC4C
Wish I could play 2moro but RCT resting me for 2 weeks!
— James O'Connor (@JamesOConnor832) February 26, 2016