Life for a goalkeeper has always been tough - and while everyone else loves a spectacular goal - it becomes tougher by the year. Petr Cech has been speaking balls to chelseafc.com.

Comparing different generations in football is a notoriously tricky business.

While the bare essentials of how the game is played have remained the same down the decades, plenty hasn't, making it best just to appreciate each era for what it was.

Recently however, there has been cause to contrast two Chelsea stars from many years apart as Petr Cech continues to excel between the posts.

The 5-0 win in our last home league game against Sunderland was Petr's 100th clean sheet for the club.

Now on 101 after Blackburn on Sunday, he has the second highest total of shut-outs in our history, clear of Carlo Cudicini's 95 plus five shared as substitute.

That's still someway below Peter Bonetti's 208 clean sheets but the Cat's took 729 games (29 per cent clean sheets). Petr's came in 181 games (55 per cent).

Our current number 1 himself spoke recently about Bonetti. 'When I arrived, everyone was talking about him,' Cech said in a Chelsea TV interview.

'I soon realised he is an absolute legend at this club and if you see the number of games Peter played and the number of clean sheets, it's amazing.'

The quality of the defenders in front of the man with the gloves, the pitches, the physical challenges allowed on keepers, the back-pass rule requiring goalies to be accomplished with their feet - these are just some of the changes over time that make Bonetti and Cech comparisons an inexact science.

Chaos theory

However, one altered aspect of the game may more than anything else accentuate the quality of Petr Cech's achievements. That's the ball he has to deal with week in, week out, and the way it is struck. And here science can be more exact.

A UK-based physicist - Dr. Ken Bray - has this year been publicising his theory on modern football flight, and arguing an unfair disadvantage hindering goalkeepers.

Many years ago footballers discovered the method of kicking a football with spin to make it bend in flight. The Brazilian-style banana shot as it was once quaintly known has been adopted across the globe.

Dr. Bray argues that keepers can read the spin of such shots and anticipate ball flight.

However now, with the latest generation of balls, players have discovered a way to hit shots hard enough (due to the lightweight nature of the balls) and with a lack of spin so turbulence builds up in the air at the front of the moving ball, causing it to change direction unpredictably mid-flight. It's the type of kick made famous by Cristiano Ronaldo but practiced by many others.

Dr. Bray asks why, when Fifa dictates the size, weight and bounce of footballs, does it not specify the aerodynamics to cut down on such chaotic behaviour.

Petr is a man who thinks deeply about his sport, and these theories back up his own experience - but he isn't holding his breath for more goalkeeper-friendly regulations.

'You can see it any time when the ball doesn't spin, the flight of the ball is sometimes completely crazy,' he agrees.

'It is very hard for the goalkeeper because the ball can move any moment from when it is hit. Then it really depends how far in front of you the ball moves.

'What the ball can do is move one way in the first phase, and then it moves completely the other way in the second phase.

'Sometimes the ball is spinning more, and at least with the indication of spin you can spot and anticipate but on the ball which doesn't spin, there is no indication, you have nothing and suddenly when it moves you are in trouble.'

All modern balls give the chance for spectacular long-range goals but Petr believes in the Champions League in particular, when an adidas ball is used, outfield players are licking their lips over how they might make the ball dance.

'That ball is really fast,' he reveals. 'You can see that there are a lot of goals that are coming from long range. Everyone shoots more, everyone knows that when it is hit very well, the ball can go.

'Last week Celtic conceded a late goal against Man United like this,' he points out, recalling Ryan Giggs heading in after Celtic keeper Artur Boruc had pushed out a Ronaldo long-range punt.

'As a goalkeeper, what can you do when the ball moves first to the right and then ended up two metres away from you on the other side?' he asks.

'I think Boruc did well even to save the ball, and then there was a rebound and everyone says what a mistake from the goalkeeper. In this case you have to see the flight of the ball and then remember the keeper is not a computer. The eye does not spot things that quickly.

'It is impossible for your body to change direction when there is movement just a few yards away.'

Now You See It

By definition, it is hard to develop a special technique to deal with such random flight above sharpening reflexes to the maximum. But Petr does 'enjoy' plenty of practice in training against hot-to-handle shots.

'Alex has such a powerful shot that it is exactly like this. Sometimes you have your hands ready in the space, the ball is five yards in front of you, and then ball is in the net and you wonder how this could happen! It does things you could never forget.'

Petr has noticed an unusual phenomenon with his own long-kicking. When he hits it above a certain speed, the ball initially flies as expected but then dies, falling at a shorter distance than a ball struck with less power.

Despite Dr. Bray's recommendation, he does not anticipate a goalkeeper's life to get any easier regarding ball technology.

'The balls are made every year to distract the goalkeepers, to give the advantage to the strikers, to score more goals.

'That is why the ball every year is getting faster and faster. You can see the number of goals coming this season from long range. Everyone understands it is a really good weapon. Everybody likes to see goals and you see the free-kicks from 25 yards, 28 yards, it is a big danger.'

Happily, so far and touchwood, Petr has a good record of dealing with free-kicks and long-range shots.

Robinho's effort that beat him in Manchester deflected off the wall. Liverpool's Daniel Agger managed to find the bottom corner with a free-kick in the 2007 Champions League semi-final meeting at Anfield and in last season's semi at the Bridge, Ryan Babel beat him from 40 yards with Liverpool on their way out. But that goal stood out due to its rarity.

'This was one of the examples,' reckons Cech, 'because it was wet and once I needed to really push hard to get back because the ball moved, I did not have much energy to jump the other way. The ball moves five yards from the keeper at 80 mph - it takes a split-second - I can't just go there.'

Orange Counting

Cech's appliance of science came to the fore in another aspect of goalkeeping at the beginning of this season when a theory of his own, that a bright orange kit would prove a problem for opponents trying to put the ball past him, was put to the test.

'So far we have a pretty nice record of not conceding goals,' he says when asked for a report on how the kit is performing.

'Whether that is because of the orange or not I don't know. It is best to ask the opponents because they are distracted, not me, or maybe they aren't.

'We concede less goals than last season so far,' is his final assessment. But why the change to black shorts after the start of the season? Personal positioning and orientation is the answer.

'For me it was too orange. The change was for myself, to see parts of my body, to feel the space. That is why.'

With that, Cech departs to face some more of this year's footballs in training, taking some of Dr. Bray's diagrams with him.

Our keeper has many years of his career ahead and life for a keeper is unlikely to become easier compared with any eras in the past. One thing is certain though, Petr will be thinking about it all the way. 

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