He had already performed beyond expectations in the course of this Davis Cup campaign but there was pressure of a different on Kyle Edmund this time around.

In July’s quarter-final the lad who had turned 21 in January had stepped into the big man’s shoes, replacing Andy Murray in singles play against a Serbian side that was itself without world number one Novak Djokovic but still boasted far more experienced campaigners in former world top 10 player Janko Tipsarovic and Dusan Lajovic, then ranked well above Edmund.

There was, of course, no doubt that he had been given an opportunity to repay Andy Murray for having led the team selflessly through their 2015 campaign after the Wimbledon champion dropped out of that tie. For all that his only intentions had been supportive, Murray’s presence as a spectator in Belgrade could only have served to underline that.

This time, though, uniquely in Edmund’s Davis Cup career and extremely unusually in that of any British player in the past decade, his job was to make up for a Murray defeat and also to justify Leon Smith’s brave call, since the captain would have had to have factored this situation into his planning given del Potro’s quality and odds which dictated that even Murray could not keep winning forever.

When selecting the team for the opening day’s play he had rejected the option of recalling Dan Evans, higher ranked than Edmund and surely oozing confidence after having taken Stan Wawrinka to five sets during which he had earned a match point during the Swiss player’s run to the US Open title.

Smith had clearly felt he had identified the necessary qualities in the younger man who could now claim the win that would put the team back on course to defend their title, something achieved just six times in the 35 years since the current World Group format was introduced.

If he could level the scores then either recent world doubles number one Jamie Murray and, if he recovered from his longest ever match, brother Andy or, if not, Dom Inglot would be favourites to put the match back into Andy’s hands on Sunday when he would be odds on favourite to win no matter who he was up against.

Defeat would, however, mean not only that the Murrays would have to do their stuff, but that Edmund or Dan Evans would have to conjure up an unlikely win against del Potro on the final day. Even without players of del Potro’s calibre to factor in, comebacks from 2-0 down are rare in the Davis Cup, achieved just 10 times in this World Group era.

Of course the same applied to Guido Pella. Following up on Juan Martin del Potro’s magnificent effort it was now the 26-year-old Argentinian’s task to avoid wasting the advantage and convert a winning start into a commanding lead.

Like most he boasted a significant experience advantage over Edmund, but only six places separate them in the world rankings, Pella 49th to the rapidly rising Briton’s 55th indicating that it was bound to be tight.

Edmund settled more quickly, breaking his opponent’s serve in the opening game, but after Pella broke back to level at three apiece both held thereafter to take it into a tie-break.

Its first half proved to be a miniaturised reversal of what had happened previously, Pella looking to have seized the upper hand this time winning the opening point on Edmund’s serve only for an emphatic drive volley winner to level it 3-3 at the change of ends.

Two powerful Edmund forehands in quick succession, the first hauling Pella out of court on the backhand side and the second taking full advantage of the available space, subsequently set up two set points at 6-4, the second of which he took with a crosscourt forehand winner.

The second set followed a similar pattern with both players serving solidly and it was consequently something of a surprise when Edmund, serving to stay in the set at 4-5 down, was broken to 30, but some consolation could be drawn from it being boldness rather than tentativeness which ultimately cost him as he over-hit an attempted forehand winner on set point.

He looked far from deterred as the third set got underway, taking the second of three break points he earned in the fifth game. However moving ahead at that stage suddenly seemed to prove more inhibiting than the setback of losing the second set had done and he was immediately broken back to love, a game completed with a weak looking double fault.

When Pella then survived a break point to hold in the next game his clenched fist indicated that he felt he had the upper hand and so it proved as he broke once again then claimed the second of three set points in the next to move two sets to one ahead.

When Pella then broke in the opening game of the fourth set the match and the entire tie looked to be in Argentina’s hands, even more so when he held serve then raced to 0-40 up on his opponent’s next service game. Edmund recovered bravely to get back into that one then survive two more virtual match points to hold after five deuces.

The coup de grace had merely been postponed, however and Pella subsequently delivered it, breaking again to move 5-2 up and racing towards captain Daniel Orsanic punching the air before changing ends to wrap up a 6-7,6-4,6-3,6-2 win that has probably decided the tie.