O'Connor will be rested for up to a month, with Toulon coach Bernard Laporte telling French media: "James O'Connor felt unwell in the bus [after] the Oyonnax game. The medical staff decided to take him to hospital and he underwent a considerable series of tests.
"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."
When he was 16, O'Connor and schoolmates were playing tackle rugby and shoulder-charging each other at Nudgee College when one boy barged him from the side.
O'Connor had not seen his friend coming and did not brace for impact. Soon after he was in agonising pain and had turned a shade of grey, and called the school nurse while in bed.
His father Warren said later that had O'Connor not made the call and gone to sleep instead, he would have passed away that night in 2006 because the blood from his ruptured spleen was flooding his stomach.
The spleen was removed immediately, and O'Connor is required to take antibiotics regularly given that the spleen is a crucial organ for the body's immune system.
It is understood that O'Connor changed the medication he was taking for this only a couple of week ago, and this may have contributed to his blackout.
