Most athletes, like most artists, shy away from analysis. They fear that intellectual understanding might destroy the creative process, that too much thinking will destroy action. Steve Davis was always an exception. This made him a fascinating interview subject when he was at his peak as a snooker player and it makes him a superb studio analyst today.

I saw quite a bit of him in the mid-1980s and relished his company. There was always something to learn because he was that rare thing — a top performer whose method was analysis. It was important for him to externalise the process. For him, some kind of intellectual control of the process of winning was essential to the art of victory.

And time and again I have seen the points he raised acted out in the daily dramas of every sport on the calendar. “You’re allowed to miss a ball,” he said. “That happens. Never get down on yourself just because you missed a ball. It’s when you start thinking wrong that you’re in trouble.”

He was to exemplify the problems of thinking wrong in his own decline. You would see him playing safe when the pot beckoned, you would see him taking on an impossible pot out of some weird sense of duty. I have observed Davis’s Law in action elsewhere and everywhere over a couple of decades since he expounded it to me. Was it in the Matchroom at Romford? The press room at the Crucible? No matter. Turn to great sport and you find a million examples of Davis’s Law.

Take the semi-finals of the Champions League this week. On Tuesday, John Arne Riise scored one of the greatest own goals of our time, giving Chelsea an equaliser against Liverpool in a fraught, first-leg match. What on earth could have possessed him to try to head a knee-high ball in his own six-yard box in the last minute of his biggest match of the season? Andy Gray used to joke — no doubt still does — about heading penalties. This was scarcely more absurd.

It wasn’t that the header was misdirected. It wasn’t a missed ball, for which Davis will forgive you. It was thinking wrong. The very idea of stooping for the header was ludicrous. It was not the action that was flawed, it was the thinking behind it.

About 22 hours later, Cristiano Ronaldo missed a penalty for Manchester United against Barcelona, and it was not the sort of miss that is forgivable under Davis’s Law. The point is not that Ronaldo miskicked, but that his penalty attempt was faulty in conception.

Ronaldo’s flaw in his bid for greatness is that he is, to use the technical term, a smart-arse. Penalties are always a temptation to such a being: the twice-taken, twice-scored, stutter-step penalty against Arsenal is a classic example. But remember that these two penalties were driven with the laces of the boot. For all the theatricality, Ronaldo hit two unstoppable shots.

Against Barcelona, Ronaldo decided to go for something more subtle. Penalty gimmicks have a way of finding you out, as Gary Lineker will tell you. He had a dinked penalty saved when he was playing for England; had he hit it properly, he might have joined Sir Bobby Charlton on 49 international goals. His failure to think right left him for ever one down.

On Wednesday night, Ronaldo’s thinking broke down. This was not the appropriate moment for showboating, for a gimmick, for cuteness. It was the moment to cut out the frills and get down to business, and Ronaldo failed. It is possible that this miss will forever mark his annus mirabilis.

One of the eternal fascinations of big-time sport is watching the way that athletes respond to pressure. Some grow into giants, others turn into midgets. Often under pressure technique goes, an easy shot is missed. Sometimes error piles on error, even for the very best. Roger Federer, the world’s best tennis player, made 54 unforced errors in his desperate victory over Rubén Ramírez Hidalgo on Wednesday.

Sometimes tension inhibits the most basic techniques in sport. Golfers get the yips, when the putting stroke fails; darts players suffer from “dartitis” and can’t let go of the dart; bowlers — particularly, for some reason, left-arm spinners — find that their action deserts them; footballers can hit the ball dead straight at any time, save when the target is the goal. But it is when tension affects the decision-making process that Davis’s Law kicks in, when the most effective, strong-minded athletes fail, not because they can’t do it, but because they can no longer think straight.

In cricket, a batsman misses a ball and gets out — that is forgivable. But sometimes he is out because he makes a wrong decision.

Shot selection, it’s called. Sometimes a batsman goes tharn, a term from Watership Down indicating the state of rabbit in a car’s headlights. Andrew Flintoff gets locked into a block-block-slog sequence, one that has nothing at all to do with the merits of the balls he is facing.

Mike Gatting, a former England captain, provides two perfect examples. In the final of the World Cup of 1987, he was out reverse-sweeping a ball from Allan Border. He was castigated for this, but I am not convinced that this was entirely fair. It wasn’t the shot selection that was wrong — Gatting used to play the reverse sweep well and often — it was just a missed ball.

But earlier in his career — and he had a very slow start in Test cricket — he was out leg-before while playing no stroke twice in the same match, both times to Malcolm Marshall against West Indies in 1984. This was clearly flawed decision-making, not flawed execution.

It is easy to confuse the two things. One of the most extraordinary Test innings of recent years was Kevin Pietersen’s assault on Brett Lee in the Oval Test of the great Ashes series of 2005. Had he got out playing one of those thunderous hooks and pulls, he would have been vilified for throwing away the Ashes, for thinking wrongly, for slogging when he should have blocked. I would probably have been among the vilifiers.

But it worked. That must mean that his decision-making was right, yes?

After all, you can’t say that that thinking was wrong, but it worked anyway. It can only have been right, and it was one of the most astonishing bits of sport I have witnessed. The thinking was right, but it was unfamiliar to those of us who witnessed it.

Sport is a Petri dish in which we examine hearts and minds and bodies and souls for signs of weakness. We put them under a lurid succession of stresses to see what breaks, when it breaks, how badly it is broken.

When technique breaks down, an error is forgivable and can be repaired. But when the thinking behind technique breaks down, when the decision-making powers cease to function, the damage is that much more profound, that much more serious, that much harder to repair. Riise and Ronaldo are for once united, undone by Davis’s Law.