The Thistles defeated the Demons 8.12 (60) to 6.9 (45) at Lilydale.

It wasn't the only surprise result as Old Launcestonians scored a 10.17 (77) to 10.11 (71) elimination final triumph at St Helens.

It means Old Scotch will meet top-team St Pats in the second semi-final and Lilydale and OLs will duel in the first semi-final.

Old Scotch hadn't beaten Lilydale this year and OLs hadn't defeated East Coast.

The Thistles led the Demons by 11 points at half-time and the third quarter proved crucial.

It was all Lilydale for the first-half of that term and Old Scotch's defenders did well to keep them at bay.

But Sonny Whiting kicked truly to put the Dees in front.

Connor Bryant's snap 17 minutes into the quarter to put the Thistles back up was pivotal.

And Aiden Jackman's snap not long after put them further ahead.

Josh Mathews received a holding free-kick at the 30-minute mark and nailed a set shot.

He let out a big roar as Old Scotch went to the final change three goals ahead.

Winning coach Brayley Coombes had high praise for his back-six.

"They were unbelievable today," he said.

"They were playing on some really dangerous forwards. But the most critical thing to them is their communication and the way they set up behind the ball and that they help our midfielders.

"They were the only line that probably didn't waver at any stage, they were solid all day.

"The midfield probably dropped off in patches and our forward line was a bit stagnant early."

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Dees mentor Colin Lockhart felt his team's lack of midfield depth hurt them on Saturday.

"I dare say our rotations in the midfield let us down with three absolute jets missing today," he said.

"Once our three mids who started in there wanted a rest we just lacked a bit of quality.

"We tried a couple of things today that were different because we've lost Thane Bardenhagen, Daniel Viney and Ty Ponting who have played in the middle all year.

"We've got three really good boys with Logan Reynolds, Reuben Rothwell and Sam Lockett.

"But then we've got blokes who have played half-forward and on the wings all year trying to pinch hit in there.

"We'll go back to the drawing board. We'll go back and go 'well, that didn't work, this didn't work'.

"That's the joy of being second on the ladder, you get that double chance. So we've moved on pretty quick."

Ponting and Viney got injured in round 18.

"Ty got concussed last week so he's a mandatory and misses a week," Lockhart said.

"Daniel got a knee above the kidney/spleen area and has been in hospital and struggling a little bit.

"So he's hopefully maybe another week or two (away).

"We should get Ty Ponting back next week."

Old Scotch sung their song with gusto and Coombes explained why the win was significant to the group.

"We feel for the last couple of years, we've become a tight unit that works hard and does a lot of stuff together," he said.

"We probably didn't get that reward for effort in the final series last year.

"It was critical just to win that first final to show the boys the hard work is starting to pay off.

"We've always been a competitive side and we're starting to get a bit more polished with our ball-use."

He said the Thistles got through unscathed.

Lockhart felt his troops battled hard.

"Everyone had a crack and today we just weren't good enough," he said.

"That's what it boiled down to, they were the better side on the day and deserved to win."

Lockhart said the Dees were struggling with their starts and would look to address that.

OLs led by 16 points at half-time of the elimination final but the Swans found their groove and were in front at the final change and for most of the final term.

Blues co-coach Richard Howe described the last five minutes.

"We got one (goal) and we got two and we had a bit of a roll on," he said.

"The boys swung Julian Rattray forward and I think he kicked (a goal) and pretty well won us the game off his own boot."

OLs have quickly switched their focus to their semi-final.

"It's do or die for us now and to tick the first one off is nice," Howe said.

"We take a bit of confidence out of losing to them (Lilydale) by a couple of goals (in round 18).

"Finals is a different game so hopefully we can continue with our momentum and keep rolling forward."

Swans coach Ned Hyland explained how the game got away from his side.

"It all fell apart within about five minutes of play late in the game," he said.

"They kicked four or five consecutive goals within five minutes.

"We had a couple of really bad passages with a bit of poor discipline that ultimately cost us a bit.

"Probably the energy we spent surging from behind to get back into the game and then get in front - a few of our players ran out of legs and steam towards the end."

Hyland also reflected on the first-half.

"Both sides started really hot and it was obvious the team that settled first would probably kick away early and that was them," he said.

"They probably found their rhythm a bit faster than we did."

While it was a disappointing end to the season, Hyland said East Coast would take positives from the year.

"Coming in at the start of the year we had two main goals," he said.

"We thought we had the team for that instant success and to set ourselves up in a position to try and win this year.

"Our other goal was setting ourselves up for the future through development of a few of our young kids.

"While with the immediate stuff we obviously fell short with and our season's over, we felt like we succeeded immensely around that youth development.

"We had a fair number of our young kids - first and second-year players - play senior football.

"We gave them some key roles and those guys did a great job.

"So when we look forward to the future, that's a really good sign for where our club is heading to with our core of 18-19 year olds."

Alex Sciulli, Joe Cullen and Howe were the Blues' best while Pearce Robinson, Scott Fenton and Corey Bosworth played well for the Swans. Field Reeves kicked four majors for the winners.

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