GREATER Western Sydney forward Steve Johnson's final JLT Community Series game hasn't gone well with the veteran concussed early in the opening term against North Melbourne.

Johnson collided heavily with Kangaroos midfielder Shaun Higgins at a stoppage and immediately dropped to the turf; with replays appearing to show the pair clashed heads.

The 33-year-old spent a minute or so on the deck before jogging groggily to the interchange, and didn't reappear in the first half.

GWS officials told AFL.com.au that Johnson had been diagnosed with concussion.

While not ideal for the Giants or their star forward, the positive news is that Johnson has just over two weeks to recover before the team's season-opener against Adelaide on March 26.

It's been a tough pre-season for the 2007 Norm Smith medallist who had thumb surgery in November and missed several weeks of skills training while recovering.

Key defender Aidan Corr suffered a hand injury in the first term, and has also been ruled out of the match.

Corr missed most of last season with an ankle injury and played just three games for the year.