The Kangaroos have been dealt their worst imaginable nightmare with full-forward Nathan Thompson to miss the 2007 AFL season after sustaining a serious knee injury in today's trial game against St Kilda.

Thompson tore the medial ligament of his left knee and coach Dean Laidley was "90 per cent sure" his spearhead had also wrecked his anterior cruciate ligament, when his leg buckled as he snapped at goal.

Thompson appeared immediately resigned to his worst fears, early in the second term of the match at MC Labour Park, as he hobbled off the ground unassisted and then lay disconsolate in front of the interchange bench.

His leg bent awkwardly when trying to snap a goal over his shoulder with opponent Sam Fisher falling across Thompson's stationary left leg while trying to smother the shot.

The Saints won 10.13 (73) to 9.8 (62) but also have a worry, as co-captain and star midfielder Lenny Hayes was reported late in the game for striking, which soured his first game of the year.

Hayes was best afield in his comeback match, after undergoing a knee reconstruction halfway through 2006, but was booked in the final quarter for striking Lindsay Thomas and now faces a delayed start to the premiership season.

Thompson's injury is an enormous blow for the lowest-scoring side of 2006, which finished 14th.

The full-forward had booted 54 goals for the season - 32 more than any other teammate and almost a quarter of the side's total.

Laidley was still trying to get his head around how the Kangaroos would replace Thompson, who was scheduled to rest the second half of the game.

"In reality he probably should have handballed the ball. He tried to snap it over his shoulder," Laidley said.

"That's footy. He was only going to play a half today and he was just starting to get a bit of touch and we've worked pretty closely with him over the last few weeks.

"It's disappointing. It's disappointing for everyone, but it strengthens our resolve as a footy club."

Recruit Aaron Edwards booted three goals after Thompson was injured, and could now find himself thrust into a major role much earlier than expected at his new club after four previous games with West Coast.

Hayes' effort, Stephen Milne's four goals and the returns of key defender Matt Maguire and ruck-forward Justin Koschitzke were the highlights for St Kilda, although coach Ross Lyon said the Saints were guilty of over-using the ball.

"For three quarters we dominated general play, our ball winning and our tackling was first- rate," Lyon said.

"In the second quarter (we had) 109 possessions (and kicked) two goals.

"We just didn't attack deep in the conditions, but we came in with a focus to share the ball and run and be up-tempo and get our confidence up a little bit, and we did that."

St Kilda are likely to give some of their more underdone stars one last hit-out in the VFL next weekend, although Lyon was unsure if that group would include star forward Nick Riewoldt, who sat out today's game.

AAP