How Juan Martin Del Potro became the most dangerous man in tennis

The Juan Martin Del Potro who a month ago single-handedly played the roles of both director and protagonist in one of the most entertaining sports dramas of the year, defeating Novak Djokovic and Rafael Nadal before dragging his exhausted body through four tension-filled sets against Andy Murray to earn Olympic silver in Rio, has changed a fair bit in the time since he last played a proper tennis schedule.

Between his 25th and 28th birthdays he firstly changed as a person, as most people do. While he had become one of the bigger personalities in tennis almost by accident, down to his unintentional lankiness and his role as the most lovable, gentle, permanently exhausted diva the sport has ever seen, he now seems a lot more conscious of the effect he has on fans, and his interactions with them are more deliberate.

Over the past week, since returning to the courts of his sole Grand Slam triumph at the 2009 US Open, the Argentine has been the biggest story of the first week and he has learnt just how much of a fan favourite he has become. When he faced Steve Johnson in their second-round match on Arthur Ashe Stadium, the American number two walked out onto his home court to soul-destroying, barely-audible applause. When the Argentine appeared across the threshold, the stadium exploded into a long, collective roar. In his interviews, Del Potro seems more willing to be a little funnier, slightly sharper and always on the ball.

On the court, meanwhile, his old form is returning. Through his blistering performances against the 21st seed Johnson, 11th seed David Ferrer and his first-round opponent Diego Schwartzman, in addition to the injury retirement of Dominic Thiem in the fourth round, Del Potro has picked up where he left off in Rio, waltzing through three quality opponents.

Although he hadn’t reached the second week of a slam since Wimbledon 2013, he has arrived in the quarter-finals of the US Open without dropping a single set. No player has played at a higher level than Del Potro throughout the first week of play.

But as with seemingly everything in his life today, the left wrist injury responsible for his three-year absence and near-retirement from the tour has changed his game in more ways than he can imagine. Though the wrist is steadily improving - after returning in February almost solely hitting one-handed sliced backhands, he now drives his two-handed backhand with a frequency approaching normal - the position he finds himself in is still not ideal.

Usually floaty, short and ripe for the picking, the quality of Del Potro’s current driven backhand is so poor that it has proven to be surprisingly effective; the rest of the top players just aren’t used to facing a shot of such low quality and that, along with the constant fear most live with of Del Potro’s forehand, has complicated attempts to break it down.

But the backhand is still a gaping hole in his game. In order to get even a fraction of the results he has enjoyed in recent months, the backhand has forced Del Potro to excel in every other aspect of his game. This means that his serve is more accurate than before, he is defending as well as he always has and, most of all, it means that he has no choice but to hit the absolute life out of his forehand.

When he defeated Nadal in to move into the gold medal match in Rio, a tearful Del Potro told the reporter that his tactics amounted to literally hitting the ball as hard as he possibly could. This was not hyperbole. Every inch of Del Potro’s 6ft 6in frame is geared towards being aggressive, the sound of a proper Del Potro forehand echoing around the stadium like a gunshot, causing gasps and near-screams. Now his forehand splatters through like a semi-automatic gun, there are multiple bullets per point and gasping is the official soundtrack to Del Potro’s matches. In order to stay ahead of his wrist-related weaknesses, Del Potro has manage to upgrade the potency of what was already one of the biggest forehands in history, and actually land it in.

As he congregated with Argentine journalists in his Spanish press conference after defeating Ferrer, the Argentine said, “I feel free”. Del Potro is playing with pure abandon, and for good reason. Ever since he was given the go ahead to return from his long layoff, it has been clear that he never expected anything out of this year. His wrist is still recovering and both the matches he plays and the immense treatment he receives between appearances on a tennis court are geared towards being ready for next year.

While most players are forced to deal with the daily pressures of the tour, Del Potro is as carefree as one can be while competing for the title in the second week of a slam. As he stares down the quarter-final stage and beyond at the only slam he has ever won, that makes him one of the biggest threats of all.