Australia back James O'Connor could be a doubt for the series against the British and Irish Lions next month.
O'Connor suffered a chest injury playing for the Melbourne Rebels against the Blues on Saturday.
The 22-year old underwent an MRI scan and tweeted his progress later on, commenting on a heavy tackle he received from Rene Ranger.
"Initial scans looking OK - nothing broken or internally damaged. Couple more scans tomorrow to tell full extent," said O'Connor.
"Painful stuff! Popped my sternum out on that kick receipt then didn't help when I got back up and had Ranger with a 40m run up coming at me..."
Able to play at fly-half, centre, wing or full-back, O'Connor is seen as a surefire starter for the Wallabies next month and a key member of the squad set to be picked by Robbie Deans.