The Sydney Swans had a 29-point loss to St Kilda at Marvel Stadium in Round 21 with John Longmire pinpointing the Swans pressure as the key factor in the clash.

The Saints' pressure was relentless at Marvel Stadium as they bucked a three-game losing run to snap the Swans' winning streak at five.

Trailing 50-32 at half-time, the Swans slotted the first two goals of the third term to reduce the margin to just six points.

But St Kilda rebounded with a four-goal run to open up a 76-52 lead heading into the fourth quarter.

Sydney got within 15 points before the Saints secured the victory with the last three goals.

“We were scored too heavily against on turnover. It was on the back of some average disposals, particularly by foot. We had 13 players with one tackle or less, we only had 43 tackles and 49%,” Longmire said after the clash.

“If you look at your intensities and what you do in the pressure stakes, generally if it’s high, you are able to execute a lot better skills. Whilst we were too easily scored against on some of those turnovers, it’s probably a reflection on the pressure we didn’t apply to the ball and ball carrier.

“We weren’t as good as what we have been all year in that area, and it flowed onto our ability to execute some of the basic skills.”

The Swans were searching for their sixth consecutive victory and will be looking to rebound when facing North Melbourne next week.

“We have played some really good footy for a while now. We weren’t at the level we would like to be and the opposition were really good, they kicked accurately and were able to feed off it and bring some really good pressure,” Longmire said.

“We would rather not need [the loss] as a reminder. It’s something we are pretty aware of what we need to bring, but if you are a little bit off, and the opposition are playing really good footy, that’s where the differentials open up in pressured skills, ability to move the ball and stop the opposition from moving the ball.”

“The reality is we have to be a bit better than that, improve that area of our game and that has been a strength of ours.”

The Swans again had to deal with disruption before the first bounce when gun midfielder Callum Mills was a late withdrawal as the teams were warming up.

Mills was also one of the four Swans players who were exposed to a COVID-19 hotspot ahead of their clash with Greater Western Sydney in round 18, and he was pulled from that match in the hour before the first bounce along with teammate Harry Cunningham, then forced to isolate for 14 days.

The 24-year-old’s late withdrawal from the match against the Saints was due to ongoing soreness in his Achilles that coach John Longmire said didn’t get the training it needed during Mills’ time in isolation.

"He’s had Achilles soreness for a fair bit of the year and we thought we were getting on top of it before he went into isolation,” Longmire said.

“It needs a bit of loading, through that period he wasn’t able to get the loading he required and he’s sort of taken a step backwards.

“Hopefully we can get him right for next week, it certainly wasn’t right for tonight. We were hopeful we could get him to be OK, but it was getting worse the closer we got to the game rather than better.”