HEATH Grundy played every home-and-away match with the Sydney Swans this season and was a vital member of the AFL's best defensive unit - and then came his moment of madness.

One week out from the AFL finals, Grundy's strike on Geelong's James Podsiadly during the second quarter of their round 23 clash led to the first suspension ever in his entire footballing career, junior or senior.

It suddenly left the Swans without one of their most important assets for a qualifying final against an Adelaide side boasting powerhouse duo Taylor Walker and Kurt Tippett.

Thankfully for Grundy, Lewis Roberts-Thomson was able to slot into his role and help secure victory and a home preliminary final against either West Coast or Collingwood.

Twelve months after glandular fever forced him to miss last year's finals series, Grundy was mightily relieved the Swans managed to cover for his absence.

"I was just disappointed really," Grundy said of his suspension.

"My whole career I hadn't been involved in anything like that, it was just a silly incident, and it was unfortunate [that] I couldn't play on the weekend.

"I had to train on Saturday, so I just chilled out at home and watched the game.

"It was pretty frustrating after playing all the games, but I was just glad the boys won and did it in a really good way.

"We played the brand of football we wanted and dictated most of the game."

While Grundy said he "chilled out at home" and watched the game, that may not be entirely accurate.

Grundy watched the qualifying final with his fiancée Elise Hill, who explained it had been a tough day, and a difficult week, for the 26-year-old defender.

"He was really devastated, missing the finals last year with glandular fever and then having to miss the first final this year as well, it didn't pan out the way we wanted," Hill said.

"We watched it at home and were on the edge of our seat for a while and then were obviously thrilled with the win once it all came together at the end.

"During the week he was obviously pretty grumpy and disappointed he couldn't be there and help, but once they won, he knew he would be there for the preliminary final, so he was OK."

Grundy will now be champing at the bit for Friday week's preliminary final at ANZ Stadium against the Eagles or Magpies.

The Swans beat West Coast in Perth in round 16 before an eight-point loss to Collingwood in round 20.

"West Coast were a little bit undermanned, they had a few of their really solid forwards out in (Josh) Kennedy and (Quinten) Lynch," Grundy said.

"Those guys are back now and that strengthens their side a little bit.

"Still to go over to West Coast [and win], we take a lot of confidence out of that, they're a good side no matter where you play them.

"And the Pies are a terrific side. It was disappointing to lose a few weeks ago, but we'll be raring to go if we have to face them."

James Dampney covers AFL news for AFL.com.au. Follow him on Twitter: @AFL_JD