This was the weekend when reality really hit home in the AFL.

For months now there has been genuine excitement that there were not one but two teams ready to not only challenge but even conquer reigning premiers Geelong.

After all, Hawthorn and the Western Bulldogs had kept pace with the all-conquering Cats through the first 15 rounds of the season - despite the fact the Cats had only lost one game during that time.

But in round 16 we finally found out the truth - Geelong is still a mile in front of the rest of the competition and the Hawks and the Bulldogs, while much improved, have not bridged the gap on the mighty Cats nowhere near as much as first thought.

The Cats' 61 point demolition of the second-placed Bulldogs - combined with third-placed Hawthorn's shock second half capitulation to St Kilda on Saturday night - are the most significant results of the season and have effectively separated the Cats from the chasing pack.

And the fact the Cats did it without injured Brownlow Medal favourite Gary Ablett as well as number one tagger Cameron Ling and late withdrawal David Wojcinski is even more ominous for those teams eyeing off the Cats' crown in September.

After this weekend's round the Cats will be unbackable to win back-to-back flags for the first time since 1952 as Saturday's game - while admittedly played at Geelong - raises the question that if the Bulldogs can't get near the Cats without Ling, Ablett and Wojcinski, what hope have they got when all three return come finals time.

The Cats' brutal demolition of the Bulldogs again raised question marks as to whether the Dogs' unconventional forward set-up - which lacks the traditional key forwards possessed by the Cats and the Hawks - is good enough to win finals in September.

Geelong's magnificent defensive pairing of Matthew Scarlett and Darren Milburn - whose 19 possessions in the first term set a new league record - simply feasted on a Dogs' attack that was exposed as lacking height and class against the league's best side.

The Cats' frightening depth was again on display as James Kelly and Brent Prismall - who would be stars in any other side but are fringe midfielders in the Cats' line-up - came in for Ling and Ablett and had 41 possessions between them as reigning Brownlow Medalist Jimmy Bartel and Joel Corey also took up the slack in Ling and Ablett's absence.

And Ryan Gamble - a 20-year-old who was playing just his ninth game and was a late inclusion for Wojcinski - booted four goals in an ultra-impressive performance.

As for Hawthorn - their second half fade-out against the rapidly improving Saints on Saturday night - also exposed question marks against the Hawks' premiership credentials.

The Hawks' problem - unlike the Dogs on Saturday - was not their attack, where they still possess the league's most potent pairing of Lance Franklin and Jarryd Roughead, but rather their midfield and defence.

With Saints' skipper Nick Riewoldt magnificent with six goals, the Saints' slammed on 12 goals to three after half-time to turn a 28 point deficit at half-time into a 30 point win.

In the process they smashed the Hawks' "rolling zone" which has protected its shaky defence admirably this season.

But with the Hawks' losing control of the ball in midfield and its defence losing the protection it has enjoyed for much of the season - the Hawks' defence was exposed for what it is and that is the team's weakest link.

The Hawks have now conceded nearly 200 points more than Geelong and nearly 150 points more than Sydney - the only other realistic premiership contender - this season and lack big and experienced bodies down back other than Trent Croad with even the courageous Campbell Brown looking undersized and vulnerable when the opposition controls the midfield the way the Saints did on Saturday night.

But all is not lost for the Hawks and the Bulldogs.

While the Cats - who now have 15 wins from 16 games and 34 wins from their past 36 matches in total - have opened up a six point gap over the Dogs and an eight point gap over the Hawks at the top of the ladder, those two teams are still virtually certain to finish second and third.

That means the pair - who remain four games safely inside the top four with just six rounds remaining - will probably meet in the qualifying final in the first week of September with the loser having the double chance and the winner most likely to emerge as the Cats' number one premiership challengers.

But as we all saw this weekend the Cats remain in a league of their own and right now it is almost impossible to envisage anything other than Mark Thompson and Tom Harley again holding the premiership cup aloft in September despite the best efforts of the Dogs and the Hawks this season.