GREATER Western Sydney fears defender Adam Kennedy tore his anterior cruciate ligament in Friday night's loss to St Kilda.

The defender landed awkwardly on his left leg during a marking contest in the Giants' shock 23-point loss, with his knee twisting inwards.

He spent the rest of the first term on the sidelines as the GWS medical staff put his knee through a full range of tests, including several ACL tests. Kennedy tried to stand up, but his knee buckled underneath him.

Five talking points: St Kilda v Greater Western Sydney

The 24-year-old limped down the race with the doctor and did not return, and coach Leon Cameron said the club is expecting to lose Kennedy for the rest of the season.

"We'll find out in a day or two, but it's not looking great," Cameron said.

"That's life. He's probably one of our most popular players and he was in really good form, but everyone has to put up with that. It's disappointing to have [Matt] Buntine and him [suffer serious knee injuries] in the last month, but that's what we've got to deal with at the moment.

"But we'll confirm that on Sunday. It's not looking great."

Adding to the loss of Kennedy and Buntine is the hamstring injury sustained last Saturday against the Bulldogs by in-form defender Nick Haynes who is expected to miss 10 weeks.

There were also concerns during Friday night’s game for Nathan Wilson after his head hit the ground heavily in a tackle during the second quarter, with the defender appearing to be given an extended concussion test on the sidelines but he returned to the field after half-time.

However, Koby Stevens may come under scrutiny from the Match Review Panel for the tackle, despite being awarded a free kick for holding the ball against Wilson.

Cameron appeared surprised that his player didn't win a free kick after being dazed by the tackle.

"He was off for about 25 minutes and had to go through the concussion test. It was disappointing to have him off the ground," he said.

"I'll have a closer look at it and I haven't seen the replay, but my understanding is if you are slung and you're hit in the head, then it's normally a free kick. But whether the umpire was blind-sided or not, it's a pretty fast game.

"But he got back up…I thought when he came back on the ground after half-time he tried to get us going again off half-back. It was a good effort from him to do that."