Another chapter is being written in the Eastlake Demons' underdog story after they set up an AFL Canberra grand final showdown against the Ainslie Tricolours at Manuka Oval this weekend.

Eastlake advanced to the club's first seniors grand final since 2010 with a 14.7 (91) to 9.12 (66) preliminary final boilover against the Belconnen Magpies at Manuka Oval on Sunday.

The Demons finished fourth this season but a win over a competition powerhouse - a week after conquering the fancied Queanbeyan Tigers - has given them a glimmer of hope that a title 17 years in the making is on its way.

"It’s fantastic for the footy club, we haven’t been in a grand final for eight years, so it’s a credit to the players and effort they put in over the whole year," Demons coach Peter McGrath said.

"Ainslie are a good footy team, we’ve had one win against them during the year and that gives us plenty of confidence. They’re a good footy team but anything can happen in grand finals.

"We’ll recover well and plan during the week and hopefully get the rewards next week."

Eastlake outclassed their opposition in the opening exchanges, with Belconnen's hold on the lead only coming on a few fleeting moments in the third term with the grand final-bound Tricolours watching from the stands.

Eastlake's dominance began to waver when Riley McMahon was taken from the field with a knee injury in the third quarter.

But the fightback was short-lived. Belconnen missed early chances in the last quarter and the Demons struck truly to put themselves on a collision course with the minor premiers.

However McMahon looks extremely unlikely to suit up in the biggest game of the year.

"He has been absolutely unbelievable for us over the last half of the season, this week and last week he has been tremendous," McGrath said.

"At this stage it looks like it’s a knee, it’s tragic for him but we have to look to try and replace him next week and step up in his absence."

The sight of Belconnen stars James Bennett, Sam Fisher and Chris York watching on from the boundary was one to forget. What the Magpies would have given for them to trade suit pants for football boots.

"I would have been loved to have been out there, being in the coaching box isn’t fun, especially when you’re in a competitive game and your boys are going so well and you can see they’re up for the fight," Bennett said.

"Coming into today, I felt like we had so much more footy left us in for the year so it’s a really hollow feeling in that you feel like the season is going to keep going, and then to have it taken away from you.

"Ultimately it’s a bit of an empty feeling because it’s a game of footy we could have won. We dominated parts of the game, we dominated around the stoppages, but we couldn't get any clean footy going into the forward line and that really hurt us."

While Ainslie's men's side is eyeing a three-peat that hasn't been achieved in AFL Canberra's senior competition since the Sydney Swans claimed four titles on the trot from 2005-08, the club has another type of trifecta on the horizon.

Ainslie's Rising Stars and second grade sides both won their preliminary finals to advance to their respective grand finals - both against the Queanbeyan Tigers.

Queanbeyan will meet Eastlake under lights in next week's first grade women's decider after keeping their premiership defence alive with a win over Belconnen.

AT A GLANCE

AFL Canberra preliminary final -

BELCONNEN 1.4 3.7 8.9 9.12 (66)
EASTLAKE 4.4 6.6 9.6 14.7 (91)

AFL CANBERRA GRAND FINALS

First grade - Ainslie Tricolours v Eastlake Demons at Manuka Oval, 2.30pm.
Second grade - Queanbeyan Tigers v Ainslie Tricolours at Manuka Oval, 12pm.
Rising Stars - Queanbeyan Tigers v Ainslie Tricolours at Manuka Oval, 9.30am.
Women's first grade - Eastlake Demons v Queanbeyan Tigers at Manuka Oval, 6pm.