T he bigger they are, the harder they fall.

The more determined they are to get back up again. It is not how the expression is supposed to finish but it seems a necessary addendum when it comes to Juan Martin del Potro, the 6ft 6in Argentine who will today take on Novak Djokovic in the semi-finals of Wimbledon 2013.

The Serb does not lack stature either, since the scale of his ability has taken him to the top of the world rankings and the challenge of blocking his route to the final is enough to make one feel a little weak at the knees. That will seem an uncomfortable statement for Del Potro given an injury to a slip in his quarter-final with David Ferrer caused him to over-extend his knee and force the match to be delayed as he took a medical timeout.

Indeed, there had been some suggestion that the 24-year-old might not be fit enough to participate this afternoon. The evidence speaks to the contrary, however, after Del Potro a light training session yesterday, while the manner in which this goliath thumped one David out in the last round with a series of pummelling forehands suggests that, while his movement may be restricted, he remains a major threat as long as the ball is within range.

He is still likely to take to Centre Court with heavy strapping on his knees – the eighth seed also collided with a chair in his third-round match – and he conceded yesterday that his ample frame had taken some punishment this summer. "I'm not going to put my body at risk," said Del Potro. "But I have the experience about injuries. I know it's the semi-finals of grand slam. All the players feel something, some pains. It's normal.

"I have my knee problem, but always the opponent, the other players, can have different injuries. You have to be strong more than the rest. The doctors tell me with this tape and taking some anti-inflammatories you can play. If they say something different, I will think."

His mental faculties will be occupied fully with Djokovic this afternoon, though, as will his nerve as he seeks to derail the progress of a player who has reached his 13th consecutive major semi-final. There is seldom any relief in collating statistics for the Serb's opponents since they cannot measure up to his form, yet there is at least some comfort for Del Potro as he won the last meeting between the pair, at the Indian Wells Masters in March and also overcame Djokovic in the bronze medal match at Wimbledon at the Olympic Games last year.

"I will need to be 100% or 110% against him. He's the No.1," said the player, who won the US Open in 2009. "He's a former champion here. It's going to be more difficult match for me but if I'm okay, if I do everything good, I will be excited to play against him.

"I remember the match during the Olympic last year on the same surface. But this time the pressure is different. I know it. But I will try to be ready and do my best."

Djokovic does not tend to leave room for such vagaries and yesterday and instead carries himself with the confidence of a man who often only meets defeat when chatting to an opponent at the net at the end of a match. Yet he has been a conscientious slam winner and freely extolled the strengths of Del Potro which he will be required to find an answer against in front of an inquisitive Wimbledon crowd.

"DelPo is a great player," said the world No.1, who overcame Tomas Berdych in straight sets in the quarter-finals. "I have a great respect for him. He's a grand slam winner but he has struggled with injuries in the last few years. But every time he comes back he comes back very strong because he just has this talent and qualities as a player.

"He's very tall, so he uses that serve as a powerful weapon. And of course there is his forehand, that is his signature shot."

Djokovic did not himself sign up to speculating about the Argentine's capacity to compete as a result of his fitness concerns, though, and instead maintained that a 6ft-plus frame contains a raw power which he does not expect to be fully inhibited. "Well, he's kind of a similar opponent to [Berdych]," he added. "You know, tall, powerful serve, quite flat shots from both sides on the baseline, and he can move around the court quite well for his size.

"So, tactically, I'm going to make few adjustments to my own game and see. I will analyse my opponent, as I always do."

The Serb will consider his path to be guarded by a sizeable obstacle. He will know, too, that it will not be so easily pushed out of the way.