Germán Denis had barely stepped off the field on Sunday when his phone began to buzz. “My word, you are strong,” read the message sent by his former Napoli team-mate Ezequiel Lavezzi. As grateful as he was for the compliment, Denis was even more thrilled by the knowledge that he would have the chance to catch up properly with his old friend very shortly. Both had been called up to the Argentina squad for the forthcoming World Cup qualifiers against Bolivia and Colombia.

That may not be such a novelty for Lavezzi, who has featured regularly for the national team since missing out on the 2010 World Cup, but for Denis any call-up remains a special event. Before being summoned (though ultimately not used) for the games against Chile and Venezuela in October, he had just five caps and had not featured for the national team since 2008. Thirty years old and now playing for a club of modest stature in Atalanta, he would have been forgiven for thinking his chance had passed.

But that was before he started scoring. The goal that had prompted Lavezzi’s text – Denis holding off his marker before clipping a surprisingly delicate finish over the Cagliari goalkeeper Michael Agazzi – was the striker’s seventh in the league this season. That’s just one less than Serie A’s top scorer Antonio Di Natale, and more than either Sebastian Giovinco or Miroslav Klose.

It is also more than Denis achieved in 25 appearances last season for Udinese, or in 29 the year before in Naples. Indeed, only once in his five seasons in Italian football had Denis scored more goals – collecting eight in 34 games in 2008-09. As much as he was admired by Atalanta’s new director Pierpaolo Marino, the man who had previously brought Denis to Napoli for a fee of close to €8m, few others believed La Dea would ever have to pay out the €70,000 bonus offered should he reach 10 goals.

At this rate, he could be there by Christmas. “Totò is untouchable, he belongs in a different category,” insisted Denis when asked if he could catch Di Natale, but even a poacher as accomplished as the Udinese striker would have to doff his cap to the Argentinian’s ruthlessness this campaign. Denis’s seven goals have come from just 27 shots – a success rate of better than one in four. For comparison, Di Natale’s eight strikes have come from 48 attempts.

Such form is long overdue for a striker who first came to Italy in 2002 – signed by Cesena for a fee of 700m Lira (equivalent to roughly €360,000) after being noted by the club’s then sporting director Totò De Falco during a prolific patch for Club Atlético Los Andes in Argentina. His time in Romagna would be, to borrow the words of the Italian magazine Max, undermined “by injury, and an uncontained love affair with piadine.” Denis got fat and, after two deeply underwhelming seasons, got sent back to Argentina.

The next three seasons would be spent with Arsenal de Sarandi and Colón, but it was not until he moved to Independiente in 2006 that his stock began to soar once more. His puppy fat now replaced with muscle, the player known as El Tanque – The Tank – powered his way to 37 goals in two seasons and earned his first call-ups to the national team under Alfio Basile, before making his summer switch to Napoli.

Marino heralded Denis when he arrived as an Argentinian Ronaldo, but that assessment instantly looked wide of the mark. For starters Denis no longer had any great interest in food or nightlife; during pre-season he even fell out with several team-mates because of his refusal to go out on the one free day they had been allowed by the then manager Edy Reja. Instead he chose to spend his time back in the hotel, speaking to his wife and children via a webcam.

But it was also true that he lacked the sharpness of Ronaldo, the cutting edge to justify such a transfer fee. In the early part of the season he was praised by Reja and the owner Aurelio De Laurentiis for his selflessness and willingness to work for the team, but increasingly the fans became frustrated at his lack of goals. In a season when not one Napoli player reached double figures, his failure to outscore even Marek Hamsik, a midfielder, was held up as evidence of his shortcomings.

The next season would prove even more difficult, with Fabio Quagliarella commanding the lion’s share of starts alongside Ezequiel Lavezzi, and a year later in Udine it would be a familiar story as Denis received only the rarest opportunities behind Di Natale and Alexis Sánchez. The opportunity to move to Atalanta, then, was seized with both hands. Marino, for one, continued to espouse his faith in Denis, describing him as “like a son”. More importantly, the striker knew that in Bergamo he would be given every chance to establish himself as the main man up front.

That he has done so in quite such style and also such a short timeframe is a testament in part to the surprising performances of Atalanta as a team – his fellow Argentinians Maxi Moralez and Ezequiel Schelotto have provided impressive support, and were it not for their six-point penalty the Orobici would be fifth in Serie A. But it is also a reflection of his power, acceleration and – so far at least – his unerring accuracy in front of goal.

Whether he can sustain such a pace all season remains to be seen, but already in Bergamo he is adored – with Marino obliged to reassure anxious fans that he expects Atalanta to take up their option to make the player’s loan move permanent at the end of the season. Denis himself has already said he hopes to stay on at the club, but for now his focus lies elsewhere. Above all else, over the next week, he hopes to give Lavezzi a reason to congratulate him again in person.