In professional tennis, comebacks are as present as the air we breathe. Players return to competition on a whim, coaches inevitably find their way back to the circus and no one seems to be gone for too long. Still, few returns have resonated as strongly as that of the past week.

Four years after his tearful final stanza as coach of his nephew, Rafael Nadal, as they clinched their 10th Roland Garros title in 2017, on Monday Toni Nadal returned to the ATP. However, when he took his spot in the Monte Carlo stands it was not in his old seat. He will now attempt to help guide the 20-year-old Canadian Félix Auger-Aliassime to the top of the sport.

Auger-Aliassime has long been hyped as a potentially defining talent of his young generation. Six years ago, he arrived on the tour in Granby, Canada as fully formed as a 14-year-old has ever been and he became the youngest player to win an ATP Challenger main-draw match. Auger-Aliassime’s game in 2015 was striking on all fronts. His athleticism – driven by his tall, slender frame – was undeniable. His serve was already vicious and he harnessed such easy power on his forehand, generated with smooth and efficient technique. As he recorded his startling early results he seemed to play within himself, with a canyon of space into which he could grow.

Even more notable than that first glimpse was how Auger-Aliassime sustained his momentum so easily. He became a French Open junior finalist at 15, the US Open junior champion just after his 16th birthday and at that same age he marked himself as the youngest ATP Challenger winner in a decade. By 18 years old, he had reached an ATP 500 final in Rio and the 2019 Miami Masters 1000 semi-finals. A sustained 2019 spring breakthrough across three surfaces culminated in a career high of 17 and as he has risen up the rankings he has demonstrated passion, drive and pleasantness.

Few have narrated Auger-Aliassime’s precocity as well as Stefanos Tsitsipas after losing to the Canadian at Queen’s Club in 2019: “It’s upsetting obviously that he’s better than me. I have to accept that he’s better than me. I might never beat him, but if I think that way, just need to wait, years maybe, for that chance to come.” Tsitsipas did not have to wait very long. He has smothered Auger-Aliassime the past three times, perhaps a reflection of his progression as Auger-Aliassime’s game has briefly stagnated.

Félix Auger-Aliassime during his Melbourne final defeat against Dan Evans this year, one of seven defeats he has endured in finals.
Félix Auger-Aliassime during his Melbourne final defeat against Dan Evans this year, one of seven defeats he has endured in finals. Photograph: Kelly Defina/Reuters

During his sustained presence at the top of the game, Auger-Aliassime’s weaknesses have become increasingly visible. He has developed one of the heaviest pairs of groundstrokes on the tour and at full flight he is supreme, but his game is heavily reliant on his offence and less varied than anticipated. He has won only 19.6% of return games over the past year, which ranks him 68th on the ATP, and during tense moments both his second serve and forehand can falter. Perhaps most notably, he seems too rigid and rehearsed. When a match veers away from him he struggles to problem-solve and make the small in-match adjustments that underline so much of the top players’ success. Matches can fall away from him at concerning speed.

Still, looking at his career from a slightly different angle can yield a radically different conclusion. Auger-Aliassime is ranked 21 in the world at only 20 years old, which is an incredible achievement in itself, and progress is often not linear – he has a long career ahead of him. His resilience counts in his favour. For example, after a dispiriting 2-6, 3-6 defeat by Dan Evans in the Murray River Open final in Melbourne the day before the Australian Open began, he admirably responded with a run to the second week as a tired Evans fell in the opening round. The defining stat of his career so far is his 0-7 record in ATP finals, having failed to win a single set in any final. The fact he is continually contesting them is a reflection of his ability in itself.

What seems clear is Auger-Aliassime has acted quickly to address any stagnation in his game and resume his rise up the rankings. After ending last season with four consecutive defeats, he split with his longtime coach Guillaume Marx and hired a renowned Canadian coach, Frédéric Fontang. His time at the Rafa Nadal Academy in Manacor last December yielded another connection as he announced his partnership with Toni Nadal last week. The hiring of such a prominent name is in itself a statement of his ambition.

As this story unfolds, it will be one of the most fascinating of the year. Having almost single-handedly moulded one of the greats, Toni Nadal will now attempt to be the difference to a young, top player in a far more subtle manner alongside another coach, Fontang, who travels with Auger-Aliassime. At some point his nephew will stand in their way.

Their first match together reflected the work to be done. On Tuesday, after the first day of the Monte Carlo Masters was rained out, Auger-Aliassime fell 7-6 (3), 6-1 against Chile’s world No 24, Cristian Garín. The Canadian had led 5-2 in the first set, only to lose confidence in his forehand and then, not for the first time in recent months, he spent 50 minutes failing to recover it. The work begins to ensure such events are in the past and he will surely relish it.