MOMENTUM in footy has always been important, but in the modern game it is now as critical to success as any other key indicator.

Identifying a momentum shift against your side is paramount - both in the coaches' box and on the ground. A team needs to react to a change in the flow of a match and the best clubs realise quicker and have more effective defensive mechanisms to help minimise the damage until the opposition's surge subsides.

In some cases the tactics put in place can actually halt an opponent's momentum.

Equally important is a team's ability to structure up to take advantage when it has control. Keeping an open forward structure and maintaining one-on-one forward contests will help keep the scoreboard ticking over when a team has the run of the match, while hitting targets inside-50 and converting opportunities in front of goal will ride home any current advantage.

These momentum shifts are occurring more often in recent years and I believe there are a number of reasons to explain this change.

The first has to do with both the pristine condition of nearly every AFL ground, including those used in one-off games. When a match in the past was played in heavy conditions and you built a lead, it was difficult for the opposition to quickly regain composure, as the contest usually turned into a slog. Nowadays, players always run on top of the ground with fluent movement.

The dynamics of the game are another reason why I believe we have such ebbs and flows. Advancement in training techniques and fitness combined with the high rotation of players ensures the game is played at a frenetic pace for every minute of the four quarters. This intensity now means that a team has the dynamics to fight back where once it was physically spent.

The modern game is played with power as its key, which means speed and athleticism is critical over the entire 120-minute journey. When I played in the 70s and 80s this was primarily the case in the first quarter, but then the game ground down to an endurance battle, realistically played at half the pace.

The third and major factor to these huge momentum swings is the sophistication in tactics now involved in the game. Each club has time to educate and train its players to identify when this change is occurring and to have precise tactics in place to either restrict or take advantage of this momentum.

Now what is occurring is that one team is 'mentally on' and dominating the contest while also getting its own way tactically. When the opposition recognise their loss of momentum and change structures, tactics and game style to adapt, the change upsets the controlling team to the degree where the momentum swings back in the other direction and then puts the other team under pressure.

It is usually the team that can either turn the momentum or make the most of the momentum that wins the contest.

Round 17 saw more momentum swings than usual. The clash between Adelaide and Essendon on Friday night is the perfect example. At half-time, with the exception of a missed shot for goal on the siren, everyone would have expected Adelaide to cruise to a comfortable victory. However, the Bombers, for the second week in a row, completely took control of the momentum and the match to win by 11 points.

Tellingly, the match told us two things - that the Crows lacked the ability to shut down the rampaging Essendon and that the Bombers are masters of taking advantage of the momentum when it is running their way.

The fledgling Gold Coast also put in a mighty performance to reel in a 36-point deficit at quarter-time and triumph by 15 points over Richmond. Granted, there was a major wind advantage but it was good to see that the young Suns hung in mentally and weren't emotionally affected by the scoreboard.

There were quite a few other teams on the weekend that drastically swung the momentum in their games but didn't obtain the victory they were looking for.

West Coast, Port Adelaide, the Sydney Swans and the Western Bulldogs all had lost control but were disciplined enough to work their way back into the game. Two of these teams ran out of time while the other two expended so much energy getting back into the contest that they couldn't maintain their momentum in the last quarter.

When you play catch-up footy you need to break the opposition by getting two or three goals in front so they believe it is a lost cause. In the case of the Eagles and Bulldogs, they both held small leads only to see the home team in front of its faithful, rally and swing back the momentum for victory.