The GIANTS has been dealt a blow ahead of its preliminary final against Collingwood at the MCG with star Lachie Whitfield ruled out after having his appendix removed on Wednesday.

The news comes the day after Toby Greene failed in his bid to overturn his one-game ban.

The GIANTS will appeal the Tribunal's verdict on Thursday so the All Australian forward could still face the Pies, but Whitfield's chances of playing again this season hinge on the result of this week's match.

Whitfield fell ill on Tuesday morning with stomach cramps and was admitted to hospital later that night.

When his condition failed to improve by Wednesday morning, he was sent for surgery.

GIANTS coach Leon Cameron said the loss of Whitfield is profound for his side, but he's hopeful the 25-year-old can recover quickly in a bid to return for a possible maiden Grand Final appearance.

"We're not going to sit here and deny that we're flat because he's not playing, and I'm not going to say he's happy about it, but it is what it is," he said.

"Is it at the wrong time (for us)? Yes, it is.

"But his health is more important than any game of footy.

"We'll be doing everything in our power to win so it gives Lachie an opportunity to play next weekend, and Lachie will do everything in his power to put himself in the frame to play.

Whitfield's illness caps a big 24 hours for the GIANTS ahead of the club's third preliminary final in four years.

Cameron said he was bitterly disappointed when Greene's suspension was upheld, despite favourable evidence from Neale that no contact was made with his eyes.

"When we went to the Tribunal last night we were really confident that we could get Toby off (the charge), and that’s why we'll appeal on Thursday," he said. 

"We think we've got a good case.

"I thought all the evidence we presented was fantastic and the case was spot on.

"Everything Toby spoke about, everything that everyone (else) spoke about Toby was absolutely spot on, and that's why we woke up this morning and we were disappointed. 

"We're also realistic about it as well, and we're confident when we go to appeal that we'll present a case and see what happens.

"That's footy, that's what happens in life, sometimes it goes your way and sometimes it doesn't."

Cameron said he's confident his players can disregard this week's distractions and focus on the biggest game of their season, just as they did last week in the aftermath of Greene's $7500 fine for his clash with Western Bulldogs star Marcus Bontempelli in the opening week of the finals.

"We've got a mature group, we've got some young kids that really look up to our leaders and they're in a really good spot," he said.

"I think that’s really indicative of the way we went about our footy last week.

"We hadn't won an interstate final and we were under siege (in the last quarter) and we found a way to win.

"You probably don't do that in those circumstances if you're not in a good spot.

"Can you replace Lachie Whitfield and Toby Greene? No, we don't have players like them on our list.

"We'll plan for Toby to play and also for Toby not to play.

"There's a lot of guys that are going to put their hands up and there's going to be opportunity for whoever comes into the team to play their role. 

"This group is very adaptable, and we've learnt to deal with a lot of injuries and setbacks over the last two or three years."