In my previous blog, I suggested that Mark Schwarzer remains pre-eminent and uncontested as our Number One. This instalment continues my assessment of Schwarzer's understudies.

The importance of a goalkeeper, to any side, is not just how well he/she stops goals from going in. There's far more to it than just that.

Football is most fundamentally a game of skill, but assuming skill levels (plus other physical attributes) are equal, football is then about strategy and communication. There are 11 generals out on the pitch and the way to win is for those 11 generals to have a common understanding of strategy (ie, A Plan) and to communicate about how that strategy should be applied in response to game situations as they unfold.

In most cases, the vital communication is the advice that comes from behind, because the person giving that advice can see what you can't see: ie, you in the game. You can only deal with threats or opportunities as you see them, but the bloke behind you can see more. If he sees a threat you can't see and calls on you to do something about it - even if it just means moving a few metres left or right - you don't question it. You respond.

The best teams all understand the game (more or less) the same way so they trust each other's judgment and respond immediately to advice. Crap teams (or teams with some crap players) don't understand the game the same way so don't trust each other's judgment - meaning threats aren't dealt with efficiently - meaning that the enemy will get opportunities to score not just through their good play but also through your bad play.

This is where goalkeepers come in. Keepers are main implementers of The Team Plan. Patrolling the very back, they see everyone but themselves in the game and the only thing behind them is the goal you are all protecting. Therefore, if the goalkeeper shouts, you disobey at your peril.

A team with A Plan wants their keeper to shout - to dominate - to strut about like he owns the place, barking instructions and calmly defusing difficult situations. That's what Mark Schwarzer brings to his professional clubs and to the Socceroos and it helps the defenders immeasurably to be guided from behind, but also to know that if the ball does get past them, the keeper's odds on to deal with it.

All of the young goalkeepers assembling credentials to play one day for Australia are adequate (and occasionally spectacular) shot stoppers, but can they inspire confidence the way Schwarzer does via their knowledge of The Team Plan and ability to move the defenders around like chess pieces to deal with the opposing Plan? At the top level, this is the key attribute that separates the Schwarzers from the pack.

Danny Vukovic (25) - has been very solid for the Mariners over five seasons and at his best has been spoken about as a potential international. Is big and strong, dominates his box and certainly does a lot of shouting, but does his shouting have much strategic influence on the players around him? From afar, it appears to me that Vukovic gives his defenders more in the way of volume than useful guidance, but the good news is that he is still very young for a keeper and can learn to have that Schwarzer-like strategic influence. No doubt he already does this, but it's always a good idea for young keepers to play sweeper in training games, to get some understanding of what last ditch defenders are up against and how advice from behind makes the job so much easier.

On the basis of the above, his move to Konyaspor in Turkey is interesting. I am not aware of Vukovic being fluent in Turkish, but I could be wrong. If he can't communicate with his defenders, how can he move them around like chessmen in response to the enemy Plan? If all the defenders can hear from behind is angry barking, they might as well have a Doberman in goal. More importantly from Australia's perspective, Vukovic won't be learning to advise his defenders if he can't communicate with them.

Full international potential - doubtful at this point, but not impossible.

Liam Reddy (28) - Definitely seems more of a communicator than Danny Vukovic, but is possibly not quite at the same level as a shot stopper. Which is more important? Shots need to be stopped but with better communication there are likely to be less of them. I suspect that as the better communicator, Liam Reddy would have a better relationship with his defenders and give them more guidance in helping to defuse difficult situations.

Having said that, Reddy seems occasionally to give vent to his anger when a goal is conceded. I'm no lip-reader, but it seems that he is possibly giving advice a bit too late and unnecessarily loud. This can undo the good work that has been done in forging the kind of relationships (built on trust and mutual respect for each others' skills) that goalkeepers need to have with defenders in order to maximise their collective goal-prevention capacity. (You never see Schwarzer bollocking his defence - he might do it, for all we know, but you never see it.)

Like Vukovic, Reddy is strong in the air and dominates the box. He had a fantastic second half of the season last year with Wellington (five clean sheets in nine regular season games went a long towards getting Phoenix into the finals) and is still young enough to mature into a much better keeper. It will be very interesting to see how he goes at Sydney this year. Probably needs to be tested overseas to improve his Socceroo chances, but a strong season could see him in the running for the Asian Cup.

Full international potential - possible.

Tando Velaphi (23) - I love watching this guy play. He's probably the most spectacular shot stopper in the A-League, but prone to the most appalling lapses of judgment. The ball that bounced over his head last season against the Mariners was one of the worst goalkeeping errors I've seen (at that level). Tends to make the odd howler and seems a tad on the light side (ie, gets bumped off in the air too easily).

But as I said, a wonderful shot stopper who regularly makes breathtaking saves that inspire me to say: "That was as good as a goal." Winning, after all, isn't just about scoring - it's also about keeping them out. Kept nine clean sheets for Perth last season and was a major reason that Perth made their first finals series.

If Tando could eliminate the errors from his game he would probably be playing overseas. Also, doesn't appear to talk to his defenders much, but perhaps that's to be expected in one so young.

Full international potential - possible.

Dean Bouzanis (19) - if a club like Liverpool have you on the books, then there's some sort of chance you can play. There's been quite a buzz of excitement about this fellow and after being described by Rafa Benitez as the best goalkeeper in the world of his age, there's little wonder.

It's hard to judge him fairly at this early stage, as he's had no first team experience with the exception of a few lower league games at Accrington Stanley. He's now established as the Reserve team keeper at Liverpool and training with the first team squad. 2010/11 could well be his breakthrough season.

Has played in several tournaments for Australia at Under 17, 19 and 23 level, but has also played three Under 19 internationals for Greece by virtue of his ancestry and remains eligible to play for Greece at full international level if we don't pick him first. I, for one, don't care much for players who aren't sure where they come from (after growing up in Australia), but we'll forgive a young man such mistakes...once.

Full international potential - very strong.

  Mitch Langerak (21) - the real deal. A mate of mine saw his debut at South Melbourne and told me: "Just watching him catch the ball in warm up, you could tell he was pretty special. Then just before kick off he patrolled the entire perimeter of the box as though he was marking out his territory. Intense."

The first time I saw him play (for Victory against Perth), he was only 19 and the Victory fans were already raving about him. He wasn't really tested that day (Victory won 4 - 0) but you could tell his class a mile away. Had to bide his time behind Michael Theoklitos and has now moved to Borussia Dortmund, but finished the last A-League season with an extended run in the Victory side and didn't let anyone down despite his tender years. His game against Kawasaki Frontale in the AFC was stunning.

This guy has it all. He's tall, dominates the box, but is agile enough to get down quickly. Is he a communicator? He speaks articulately about football and the art of goalkeeping, so that augurs well. And as we saw so recently in the World Cup, the German development system is ausgezeichnet, so there's probably no better environment for Mitch to grow into the finished product.

Full international potential - almost certain.

There's no doubt that Australia can produce fantastic goalkeepers. It's probably the only position on the park where a number of world class (or potentially world class) players regularly compete for the spot (and have done for the best part of 20 years). None of the players mentioned in this blog would look out of place in teams playing in substantially stronger leagues and all would walk into just about any other Asian national side.

Looking ahead four years, I'm going to reveal myself as a heretic by suggesting I don't think Schwarzer will still be there (at 41). In all likelihood, Federici and Langerak will be slugging it out for the honour of standing in Australia's goal, with (hopefully) Bouzanis and maybe even Velaphi keeping them honest. At that level, there won't be much between them when it comes to physical attributes, shot stopping, positioning, distribution etc. The crucial difference will come down to their personalities and game intelligence. How quickly will they perceive unfolding dangers and how well will they help their defenders get into the right positions to do something about it?

The non-goalkeeping public (and sometimes, the selectors) remember the flashy dives but they may not appreciate the smart keeper who gets along with his defenders and puts them in position to deal with threats before they become critical.

The easiest save is the one you don't have to make.

Adrian Deans is the author of Mr Cleansheets - published by Vulgar Press, distributed by Dennis Jones and Associates and available in all good book stores.