PRIMETIME will be gut-check time in round two.

On Thursday and Friday night, the AFL's fiercest rivals and its biggest premiership threats do battle in fixtures that have been turned on their heads after a surprising opening weekend of the season.

Carlton faces the old enemy Collingwood at the MCG on Thursday evening, while the very next night at GMHBA Stadium, Geelong hosts a Brisbane side it bested in last year's preliminary final.

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Remarkably, perhaps more so for the Cats and the Lions, all four go into these blockbuster primetime fixtures with a 0-1 record and at serious risk of their once-promising campaigns being derailed before they began in earnest.

In recent seasons, a handful of sides have proved that a 0-2 start isn't the death knell on the year ahead that it once was. Indeed, in four straight campaigns now, a 0-2 side has gone on to make the finals.

The Western Bulldogs did so last year, an extra-significant achievement considering the truncated 17-game season, while Essendon, Collingwood and Sydney had also done it in the years prior.

However, if the last decade has shown us anything, it's that starting the year 0-2 very rarely leads to anything positive.

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A total of 58 sides have suffered the disappointment of a 0-2 start since 2010, with only five of them – the aforementioned teams, plus Sydney in 2014 – going on to play finals football.

While both the Swans (2014) and the Magpies (2018) played Grand Finals in the same year, their chances of securing premiership success were always going to be slim.

In fact, just four teams have won premierships after a 0-2 start in the entire history of AFL/VFL football, with North Melbourne's side of 1999 the only team to do so in the past 45 years.

North Melbourne in 1999 is the only team of the past 45 years to have won a flag after starting the season 0-2. Picture: AFL Photos

The Swans (2017) made it into the second week of September, while both the Bombers (2019) and the Bulldogs (2020) were bundled out of the finals series at the earliest point after scrapping to make the top-eight.

It will mean that at least two sides will wake up on Saturday morning extremely nervous. For either Geelong or Brisbane, they would do so after suffering significant upsets against wooden spoon fancies Adelaide and Sydney, respectively, last weekend.

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Both teams made the final four last year and had been strongly backed as top-four candidates again this season, particularly after Trade Periods where they attracted players like Jeremy Cameron and Joe Daniher.

Geelong players leave the field after their upset loss to Adelaide in round one on March 20, 2021. Picture: Getty Images

For both Carlton and Collingwood, they entered season 2021 knowing that finals football would be seen as a minimum expectation among supporters rather than being viewed as something of an over-achievement.

However, each had their own issues last week. Despite getting close to Richmond and the Western Bulldogs, respectively, there was a sense internally among both clubs that the final margins might have been flattering.

All four sides, therefore, have a lot to prove on Thursday and Friday night. But two of them will wake up on Saturday morning having left themselves with an even bigger mountain to climb in order to salvage something from the 2021 season.