Forward Jonny Patton has withdrawn from the GIANTS’ clash with Melbourne, replaced by recently re-signed youngster Harry Himmelberg.

The power forward has been ruled out with hamstring tightness after pulling up sore after Wednesday’s main training session.

Patton was tested at training in Sydney on Friday morning with the club opting not to risk the goal kicker.

"He probably could play, but he only got through about 85 per cent of training," Ward said.

The 194cm Himmelberg, 21, has played six games with the GIANTS since last year's debut. On Friday morning the club announced that Himmelberg has put pen to paper on a new two-year deal with the GIANTS.

While Patton is a big loss for the GIANTS, they add almost 700 games' combined experienced through Steve Johnson, Shame Mumford and Brett Deledio.

Deledio will play his first game for the club after 243 games with Richmond.

The star midfielder has been plagued by calf injuries which have kept him sidelined in the off-season since switching to the GIANTS.

"You don't play 240 games without hard work and he's done that ever since he walked into this football club," Ward said.

The GIANTS' decimated forward line ramps up the pressure on Rory Lobb to perform in his 50th game.

"He's had some games he hasn't performed at his best but, overall, he's had a pretty good year," Ward said.

"He's ready to step up for us, especially without Jon."

The third-placed GIANTS are looking to protect their spot in the top four, while Melbourne, sitting seventh, are desperate for a win to stay in the eight.

The GIANTS take on Melbourne in the nation’s capital on Saturday at 1:45pm at UNSW Canberra Oval. Click here for tickets.