Taken to the brink, Albury showed its quality and courage to ultimately chase down Gundagai in a fabulous Group Nine preliminary final in Wagga.

Down 24-16 with 16 minutes to go, the Thunder plumed the depths of their energy reserves to blast on three unanswered tries to march into the Group Nine grand at Equex Centre on Sunday.

With the Tigers wilting under the spring warmth, and oppressive pressure, the Thunder steamed home 33-24 to set up a shot at an historic third straight Group Nine title.

Five months on from the start of season, the two most dominant teams in the Group Nine competition will face off the crown - but Albury coach Josh Cale knows it was a perilously close call.

As the Thunder-throng celebrated getting a crack at Southcity in the premiership decider on Sunday, Cale's reaction was as brief as it was priceless.

"Just," he said without the slightest preamble.

Nothing else was needed - the response was graphic enough.

Like the Thunder-throng, Cale realised his team had walked a tightrope without a net before snatching the chance to complete a stunning hat-trick of Group Nine premierships.

Bolting with a 16-0 lead inside 18 minutes, the Thunder stumbled into a football chasm before clawing their way out again.

By the time Gundagai had scored four successive tries, including the first of the second half, the Thunder were trailing 24-16, and clearly on their heels.

Amid the post-victory tumult, Cale admitted the Thunder had been on the verge of being shunted into the premiership abyss.

"Momentum is a wonderful thing," he said.

"We had, lost it, got it back and won the game."

Likewise, the Tigers rode a similar path, but hit a brick wall when the door to the grand final was almost open.

From the start to the finish, the Tigers gave as good as they got, but were also brittle at the worst possible moments.

Gundagai fought a pitch battle with Albury in the first half, but the Thunder still blew the game apart in seven furious minutes.

Denied a try when hooker James Luff was held up over the line in the eight minutes, Gundagai was subsequently shaken by three blistering Thunder strikes.

Exploiting mindlessly woeful defence near the ruck, Albury cracked the Tigers in the 12th (Willie Heta), 14th Cameron Breust (14th) and 19th minutes (Heta again) to be up 16-0.

Refusing to crumble as the team did a fortnight ago, Gundagai hit back with tries to Dane O'Hehir (22nd minute), Luff (30th) and O'Hehir again (40th) to miraculously hit the front 18-16 by half-time.

When Scott Smart scored the first try of the second half to put Gundagai up 24-16 the Thunder were in serious strife, but the game change yet again.

Just as they had done in the first half, playmaker Heta and hooker Adam Coote turned on a spectacular show to lift the Thunder over the line.

Given a sniff when Chris Seaton scored a critical try in the 65th minute, the Thunder found inspiration when Coote wrestled away from three defenders to snatch a try five minutes later.

Yet again, Coote did the damage in the 76th minute before putting Heta over for the clincher.

Looking ahead, Cale said Saturday's result became totally irrelevant.

"Nothing that has happened this year will matter next week (Sunday)," he said.

"It's a new ball game."

Which is just as well as Southcity is 3-0 over Albury in 2015