The
Greene – who is battling a foot injury – did not play in the Giants' 10.17 (77) to 5.13 (43) victory over Brisbane on Saturday at Spotless Stadium.
His absence from the GIANTS team at Thursday's selection raised eyebrows and he has since been sighted wearing a moon boot and using crutches.
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Cameron said the star forward would miss "a bit of footy".
"I don't think anyone in our medical team can say with confidence is it going to be two weeks, is it going to be four weeks, is it going to be six weeks," he said.
"Clearly he's had a poor pre-season in terms of doing the work that we wanted him to do because of the issue with his foot through the months of December, January and February.
"We got him up for round one, he was going really well. He had a hamstring issue but then come Wednesday last week he started to feel a little bit
"We've checked that out on Friday and got the results today. It's a little bit hot in one spot."
Greene, 24, missed rounds two and three due to a hamstring injury.
Cameron confirmed the nuggety forward, who booted 45 goals last season, had not fractured his foot.
"But he's probably going to miss a little bit of footy," the coach said.
Greene's absence will further disrupt the GIANTS' forward structure, which already has several band-aids on it.
Rory Lobb (knee) has not played since round three and Jonathon Patton, who is usually a key target inside 50, has had to shoulder a significant ruck burden in his absence.
Patton did not kick a goal against Brisbane while the Giants' other big forward, Jeremy Cameron, slotted only one. Young 194cm forward Harry Himmelberg also kicked a goal.
The coach admitted his forward set-up was "concerning".
"I think we've got to remember Harry (Himmelberg) is only a young kid who is working his way through," Leon Cameron said.
"He's trying to hold down a key position and we've got to be really patient with him."
