THERE is heartache among the elation for Greater Western Sydney following its upset victory over ladder-leaders Melbourne on Saturday, with promising young defender Jack Buckley struck down by a suspected ACL injury.

The 23-year-old, who has emerged as one of the Giants' most talented young prospects this season playing every game for the campaign thus far, was carried from the field in the opening stages of his side's clash against the Demons with a nasty knee injury.

Buckley jumped in a marking contest with Melbourne midfielder James Harmes, who fell across his left knee, with the 193cm defender requiring assistance from trainers to leave the ground.

It soured a thrilling nine-point win for GWS, which moved Leon Cameron's side above the reigning premiers Richmond and into the top-eight on the AFL ladder and resigned Melbourne to just its third defeat for the year.

"I saw him at half-time really quickly," Cameron said of Buckley afterwards.

"We're probably fearing the worst right now. He's off at the hospital having some scans. It's just heartbreaking sometimes when you see these injuries, especially for a kid that has put so much into his footy over the last few years.

"He's come from nowhere. He's come from being a rookie, to being a bona fide AFL footballer who holds down a key position in our backline.

"We lost Lachie Keeffe seven or eight weeks ago, which was disappointing. The indicators are that we'll probably lose Jack for a fair period of time as well. It doesn't look good.

"He's a really popular kid and that's the heartache for today. The emotion and the joy of winning at the MCG against a great team in Melbourne … but five minutes afterwards, you realise you've lost one of your great young fellas that has made so much progression."

The GWS victory was inspired by veteran Shane Mumford's return to the team, with the hard-hitting ruckman finishing with 10 disposals, a game-high 26 hitouts, five tackles and four clearances.

However, having played just one match in the four weeks before Saturday's victory, whether the 34-year-old retains his place in the side for next week's clash with Gold Coast is another matter.

"Answering that question is extremely hard," Cameron said.

"His back has been playing up and clearly his knees as well. He actually had three weeks off between efforts this week. I know it doesn't sound right, because you'd like to play your ruckman back-to-back.

"He may get up, depending on whether it's a seven- or eight-day break next week, I'm not sure. I'm also mindful that Matthew Flynn is really working on his craft with young Kieren Briggs.

DEMONS v GIANTS Full match coverage and stats

"Seeing these guys get games, knowing that Shane is not at the front-end of his career and is right at the back-end, we'll juggle that every week. But also, there is a key indicator and that's whether Shane can get up and play footy.

"He's such a warrior for our footy club and I thought he was terrific today against the best ruckman in the competition in Max Gawn. He just keeps finding a way. He grinds and he grinds and he grinds. That summed up our win."

The defeat means Melbourne is now at risk of losing its place on top of the AFL ladder, depending on whether the Western Bulldogs can overcome the last-placed North Melbourne on Sunday.

It also continued a worrying run of games for the Demons, who have now lost three of their last six matches on either side of the bye and are in the midst of a three-match run where they haven't kicked more than 70 points in a game.

Those issues forward of the ball could lead to Melbourne coach Simon Goodwin recalling either new recruit Ben Brown or the out-of-favour Sam Weideman for next week's important clash with Port Adelaide.

"It's certainly something we'll look at, there's no question," Goodwin said.

"If you look through the history of the season, we've lost two games playing three talls and one game playing two talls. But we're not naïve to the fact that we probably need to execute better inside-50 and we need to score a little bit more.

"It's something that we'll continue to look at. The key thing is that those guys get themselves in really good form and that will give themselves the best opportunity to play.

"We're just going to continue to find ways where we can execute better and build our game and today wasn't that. There were too many areas, especially in that first half, that certainly weren't to the level."