Reginald Brace at Wimbledon: Murray to exploit chinks in Nadal's armour

The first is the condition of the Majorcan's rally-worn knees which are such a source of concern that he has withdrawn from his country's Davis Cup team to play France. The second is the less than imperious form Nadal has shown in the early rounds at Wimbledon.

Robin Haase, of Holland, extended him to five sets in the second round and Germany's Philipp Petzschmer repeated the process in the third.

True, Nadal extricated himself on both occasions, and has played with more authority since then apart from a hesitant start to his quarter-final against Robin Soderling.

But the inescapable fact is that there are chinks in Nadal's armour. The 2008 Wimbledon champion is not bulldozing opponents out of the way. He is struggling a bit, although, to be fair he is the sort of warrior who seems to draw strength from toil.

Nadal came to SW19 after winning his seventh grand slam title in the French Open last month. Murray's morale-boosting run at Wimbledon followed a barren spell in which he failed to win a title in the first six months for the first time in five years. His last victory of any significance was in the Australian Open quarter-finals – against Nadal.

Belief that he can rekindle the form he showed in Melbourne in January holds the key to the outcome today. He must have consistency, an unflappable reliability of shot, and a resolute attitude irrespective of the situation. Which is easier said than done, as any tennis player, from hacker to hero, will tell you.

What do you do to avoid becoming locked in the protracted rallies which are Nadal's stock in trade or negate the Spaniard's devastating forehand, not to mention the sliced backhand which soaks up, indeed relishes, pressure?

Well, there is nothing more encouraging than a steady supply of cheap service winners so it is vital that the British No 1 is on top serving form.

Keeping the ball low is another must because there is nothing that Nadal likes more than a high bounce which leaves the ball sitting up invitingly for the blow he is only too happy to deliver.

Drop shots must be used with caution given Nadal's electrifying agility, and forays to the net will have to be well timed and decisive in view of his gift for clouting passes from the most outlandish positions. Nevertheless both tactics have to be employed, along with dinks and angles, to break up the pattern of play.

Despite the nagging injuries, Nadal remains the most insatiable workhorse on the tour. No ball goes unchased and rivals despair at putting the ball out of his reach. It takes the sharpest of angles or the fiercest of shots to prise a point from his grasp. When he does lose an exchange, the agony is etched on his face.

Murray, firing on all mental and physical cylinders, can become Britain's first men's singles finalist since Bunny Austin in 1938. But it will take a sustained effort by the 23-year-old Scot if he is to go one better than he did last year when Andy Roddick proved his undoing. Versatility under pressure could hold the key and there will be no room for temperamental lapses.

Finally, let us leave it to the two players to sum up their prospects. "If I serve well and play like I have been, I've got a chance," said Murray. "Psychologically, I need to believe that I can win the match. That's the most important thing.

"Apart from that, you don't want to leave the ball in the middle of the court on his forehand. You've got to serve well, keep a good length and play well – really well. I know it's going to be an incredibly difficult match, but it is one I believe I can win."

And here's Nadal on the contest: "I'm going to have a difficult match against Andy but I am ready to try my best to reach the final.

"I have to play at my best level if I want to win. So we will have to see what happens. My physical condition is fine and I'm happy how I'm doing."