Graphic: how tall is too tall?

Graphic: the men's singles draw

Nobody who regularly observes the upper reaches of the men’s game doubts that Juan Martin del Potro is on the threshold of great achievements. He has the bearing of a champion, is serious and hard working and among the small group who can legitimately aspire to replace Roger Federer and Rafael Nadal at the summit he is the youngest, the biggest and the strongest.

According to Federer, Del Potro “has made considerable progress and I’m certain he’s going to be a great player in the future”. That assessment was made shortly after Del Potro took Federer to the five-set limit in the semi-finals of the French Open, a match Del Potro dominated for three sets before his stamina ran low, hardly a black mark against a 20-year-old.

Nadal’s uncle and coach, Toni, is another admirer of the giant Argentine. “He has the personality, ambition and potential to get to the top of the world rankings,” he said. “He had an amazing year last year, so we knew he would turn into a dangerous rival.” Toni Nadal was referring to a streak of form that included 23 wins in a row and took Del Potro from 65th to 13th in the rankings. Since then he has risen to No 5 and taken several notable scalps, including Nadal’s in the Masters Series event in Miami.

Del Potro’s great leap forward began after last year’s Wimbledon and his notable wins have been on hard courts, on which he has won three ATP tour titles, and clay, on which he has won two. Which prompts the question: can he do it on grass? Could he possibly be Wimbledon champion?

In two visits to Wimbledon, Del Potro has hardly set the turf alight. On his debut at SW19 in 2007, he beat a clay-courter in the first round and ran into Federer in the second, losing weakly. Last year, another Swiss, Stanislas Wawrinka, beat him in straight sets at the same stage. But his Wimbledon seeding of No 5 underlines that it would surely be a mistake to dismiss Del Potro as one of the legion who regard the small window of the grass-court season as an unwelcome interlude.

With a mighty and varied service and tremendous athleticism, Del Potro has the raw material to blast his way through to the business end of the championships. If he were to win, Del Potro, at 6ft 6in, would be the tallest Wimbledon champion of them all. And therein lies the conundrum.

Historically, the champions have grown taller as the decades have passed. But this is not basketball. There’s a limit, a point at which the obvious advantage of serving cannonballs from a great height is outweighed by limited flexibility and difficulty in bending to the low bounces encountered on grass.

The example most cited is that of Ivo Karlovic, at 6ft 10in the tallest man to play the Championships. He is a man-mountain with a serve to match but the rest of his game is limited and brittle. In 2005, he served 51 aces in his first-round match against Daniele Bracciali (5ft 11in), the Wimbledon record, and somehow managed to lose. When Karlovic goes on court with another big server, such as Andy Roddick, every set is decided by a tiebreak and you wonder why they bother with the games that precede them.

Karlovic is too big and these days just about everyone under 6ft is too small. It seems hardly conceivable that a man as short as Rod Laver (5ft 8in) could win the title today. The smallest man ever to compete at Wimbledon, incidentally, was Felicisimo Ampon of the Philippines, who was 4ft 11in. In 1952 he took Frank Sedgman, who won the championship that year, to five sets.

So is Del Potro too big? Or, to put it more precisely, is he too inflexible? Not in the view of Tony Pickard, who coached Stefan Edberg (6ft 2in), that incomparable exponent of serve and volley, to three Wimbledon finals, with two wins. “Del Potro looks to have the perfect frame, from top to bottom,” Pickard said. “He’s a very fine athlete, a thoroughbred. He moves really well, so his size doesn’t count against him. But to take full advantage of his height and power he needs to learn to move forwards as well as sideways.” In Pickard’s view, Del Potro must serve his grass court apprenticeship.

“These days, with the players staying mostly around the baseline, the movement is all lateral. The art of moving forward seems to have gone. When Wimbledon came round, I used to say to Stefan, ‘When I see you moving to the net, you’re not fast enough. When I see you floating there, you are quick enough’. To play serve and volley, it is essential to make your first volley from a metre or more inside the service box. It’s the difference between hitting your first volley from around your ankles and hitting between your knee and hip. When you have a higher volley, you can do what you want with it.

“I think it’s important for Del Potro to serve and volley at least some of the time. Otherwise, his opponents can knock the ball back without worrying about where he is. And he can volley, all right. He showed that in Paris. He has a super serve and he can move his opponent around with his second serve. That’s what Stefan did and it gave him that extra time to close in on the net.”

If Del Potro is to make a serious attempt at winning Wimbledon, he could do no better than watch video recordings of Edberg, a master at getting to the net, closing the angles and delivering the killing volley. Del Potro has the serve, the power and the athleticism.

What he needs is mental flexibility. He needs to learn to love grass and to adapt his game to its requirements. If he can manage that, he can take the next big step from being a danger to becoming a Wimbledon champion.