GREATER Western Sydney defender Nick Haynes will miss the Giants' season-opener against Sydney as the club investigates a stomach concern for the All-Australian.

Haynes has been working through some stomach issues that have limited his training in recent weeks, however he stepped things up in a session on Wednesday at Accor Stadium.

It wasn't enough for him to be ready to compete at AFL level, though, with the 2020 Therabody All-Australian backman to play in the Giants' VFL practice match on Saturday against the Swans.

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Coach Leon Cameron said the important 29-year-old could line up in round two. 

"With Nick, we’re managing some stomach issues that have come up in the past month or so," Cameron said. 

"He's been assessed by a number of specialists to see if we can get to the bottom of them to allow him to compete at the highest level. Right now he’s getting a fair bit of training in and he's not far off, but he's not quite there for AFL footy.

"He's our All-Australian and when he's ready he'll be in our team, that could be as early as next week."

Haynes has been a mainstay of the Giants' backline for nearly a decade, playing 166 games for the club. He was a joint winner of the Giants' best and fairest in 2020. 

The Giants take on Sydney at Accor Stadium in the Saturday twilight slot. The clubs' remaining players will take part in a practice game earlier in the day, however the suspended Toby Greene will not play in the game.