"COACH Killers" is a fun segment run by ex-Richmond coach Danny Frawley on the Fox Sports program After The Bounce. It is also a term increasingly becoming part of the footy jargon.

For the uninitiated, it is a phrase used to describe those absolute on-field clangers which can, in a colloquial sense, kill a team's winning chances and subsequently kill a coach's career.

They are very visible and they create great frustration for coaches and fans alike.

Much more subtle, much more difficult to understand, but just as disconcerting, are large fluctuations in on-field performance.

I have always believed that the level of performance produced in a game of football comes from an indefinable balance of physical, mental and emotional. 

The physical is simply the ability of the body to do what it is asked to do. It's a combination of speed, strength, endurance, balance, hand-eye coordination etc.  Injuries or illness aside, physical capabilities can't alter that much from week to week.

Mental is the ability to think clearly and make effective decisions. It is perhaps observable, but not measurable. Again, the mental level can't change that much in the game-to-game cycle.

Emotional, broadly speaking, is the level of desire, determination, composure, confidence and belief.

It is the emotional state of individuals and teams that can and do fluctuate enormously over quite short periods of time, even from quarter to quarter as we see so often during every round of footy. There was no better example than Hawthorn coming from well down early in the last quarter against Fremantle last Sunday to kick eight unanswered goals to salvage a win.   

To further complicate an already unpredictable set of factors that has a huge bearing on a team's level of performance is the very fact that these same varying factors will also be heavily affecting the opposition.

The most obvious reason for fluctuating performance is that we are talking large teams of human beings, not unemotional. The challenge of achieving consistently high output is never the less an essential part of the coaching art.

Even after 20 years of coaching, I could never accurately predict the level of player readiness because the optimal emotional state is such a delicate beast.

As happens every round of footy, last weekend we had various examples of coaches who no doubt were asking themselves why their team's performance had fluctuated so dramatically.

How, for example, can you possibly rationalize the Brisbane Lions, who went from their best half of the season against the Crows in Adelaide straight into their worst half against Sydney.

There is no logical rationale except what is so often underestimated - the opposition performance.  Quite possibly, while the Lions were having a terrible half, the Swans were having one of their best.

Also, there was a Melbourne side which, in seven days, went from looking non-competitive when well beaten by Carlton in round 10 to a side with enormous energy levels and great attack on the footy in an excellent round 11 win over Essendon.

Clearly, the inclusion of quality young guns Tom Scully and Jack Trengove was a positive factor. Likewise, the galvanising effect of the 'bruise free footy' tag with which they'd been labelled in the wake of the loss to the Blues.

But the difference in seven days was extreme.

So, too, was the Essendon performance. Looking nothing like the brilliant Collingwood clones of the March pre-season, they seemingly have fallen victims of their own early peak, and the fatigue that can often follow. The Bombers drop in form, even allowing for the absence through injury of Jobe Watson, may have a physical catalyst.

As a team, the Western Bulldogs have degenerated enormously from the top four side of the last three years.

There is a multitude of contributing factors to the Bulldogs demise but the best individual case study is Brian Lake.

In the space of a few months, he's gone from last season's All Australian full-back to a battler who can hardly get a game.

He's had an injury-disrupted preparation, and he's reportedly had some troubling off-field business issues.

But if he was recruited from another sport, we'd be saying "bad experiment - he knows nothing about the game - he's got no hope".

Whatever the catalyst, it is sad to see such a quality player in this huge emotional hole.

Lake has gone from an attacking defender who was prepared to leave his opponent to go at the footy to one who is so totally devoid of initiative that he is simply following forwards around, not attacking the footy and not defending with any conviction.

At one stage against Geelong last Saturday, Lake came out from full-back to meet the footy, but instead of bending down to pick up the bouncing ball, he tried to kick it. Even Karmichael Hunt has learnt in his first season in AFL that is terrible decision-making.

With the Bulldogs being soundly beaten all over the field and Lake struggling down back, the deck chairs were shuffled and he was sent into attack where after a couple of fumbled chest marks, he eventually took a few grabs and kicked three goals.

Truth be known, this extraordinary fluctuation in physical capability and mental indecisiveness, and the ensuing ebb and flow in confidence and belief that we see so clearly in Lake's recent form is going on, to some degree, within almost every player in the competition.

This is where the emotional qualities of resilience, stability and mental strength are essential to flatten out the difference between good days and bad days. From a team perspective, experience, discipline and strong leadership is what consistency is built on.

My coaching attitude has always been that because the emotional side of the game is immeasurable and difficult to control, the focus has to be on getting the perfect physical preparation and developing the instinctive habitual actions that lead to consistent success.

And if a player has faith in his preparation and match fitness, has developed good habits and  believes in the team plan, a positive emotional state tends to follow.

The views in this article are those of the author and not necessarily those of the AFL or its clubs