PAUL Roos lamented the lack of effort and intensity displayed by his players after the Sydney Swans fell to St Kilda in Saturday night's season opener.

After a bright start that saw them lead by 27 points at the first break, the Swans failed to register a goal in the second and third quarters, which the coach put squarely down to a lack of commitment.

"You can talk about tactics and where the game's going with the rolling zone and all those sorts of things, but the one common theme in footy is it's all about effort and intent," said Roos, who was at a loss to explain the lapse.

"Our effort was very high in the first quarter, dropped off in the next two, and picked up in the last. If you're fluctuating [like that] it makes it really hard to win.

"The history [of our team] is as soon as our effort drops off we struggle with our ball use, we struggle with our decision making, we lose our match-ups and all those sorts of things. That really hasn't changed for us as a footy team for six years.

"If we don't get probably 15 guys playing really good footy then we struggle to win against anyone.

"We've probably had worse losses, but I don't think we've had back-to-back quarters like that."

The final margin of 15 points flattered the Swans, who were soundly beaten through the middle part of the match, but Roos declared most of the players who ran out against the Saints would be given a chance to redeem themselves next week against Hawthorn at ANZ Stadium.

"It's a long season and it’s one game,” he said.

“You're always concerned when you lose and you make adjustments during the week, but most of the guys who played tonight will get another chance next week.

"You continue to play them, but at some point if they can't do it then you start to replace them with other guys. It's certainly not at that stage yet.

"We played a team that's been picked to play in finals and be top four and all those sorts of things. At this stage it's a loss and you move on to next week and you play most of those guys again and give them another chance."

In a performance with few positives Roos agreed Craig Bolton's defensive job on St Kilda skipper Nick Riewoldt was a highlight and, to a lesser degree, Lewis Roberts-Thomson's effort on Justin Koschitzke.