Gameiro suffers serious knee injury
Gameiro was selected as part of a 22-man squad that travelled to China to take on Brazil, Korea Republic and the hosts.
The Olyroos drew 2-2 with Brazil in the opening game, lost 3-1 to the hosts China before ending the tournament on a high with a 1-0 win over Korea Republic.
The Sydney FC attacker suffered the injury in the game against Korea Republic in which he started but only lasted a quarter of an hour.
Sydney FC coach Graham Arnold confirmed the serious injury but is still unsure of the extent of the damage.
"Bad news is that Corey Gameiro looks like he's done his ACL," Arnold said. "I think he lasted 10 or 15 minutes. The kid is absolutely devastated.
"I'm confident Corey will come back even stronger than before, he's got the mental strength to do that, but it's could be a long lay-off and I just wish him a speedy recovery.
"At this moment he's at the doctors getting the scan. The medical staff at the FFA rang me straight after the game and they're 80 per cent certain.
"I don't know how it happened, I just got the call, but we've got the depth and we've got the cover so we'll get on with it but it's sad for the kid.
"It's a big loss because the kid was doing so well. He was scoring goals and working hard and he was having a very good season after a bad season last year so it's devastating."