Knowing the austerity with which Cristiano Ronaldo approaches his diet, it feels improbable that he ever even had the culinary context to compare sticking the ball in the net to getting ketchup out of a glass bottle. Eight years ago, when he entered the World Cup on the back of a 16-month scoring drought for his country, he assured reporters that once the seal was broken, the goals would readily flow.

It did not really happen for him in South Africa, Ronaldo chipping in once before Portugal went out in the last 16. Since then, though, he has scarcely stopped scoring. The giant Nike billboard raised in Turin’s Piazza Veneto in recent days reminds us of his greatest hits – from becoming the fastest player ever to score 350 times for a top-tier European club, through to his status as the most prolific player in European Cup history.

The wait goes on, though, for his first goal as a Juventus player. A sellout crowd had packed in to the Allianz Stadium for his home debut on Saturday expecting to see precisely that. Each time he put the ball in the net during the warmup, they roared as though it were the real thing.

This was a peculiar occasion: an ostensibly tricky fixture against a Lazio side that had won here last season, yet with an atmosphere that felt more akin to a friendly. A whole city had been counting down to this moment ever since the day of the World Cup final – when Ronaldo snuck into town to complete a move that even the most optimistic fans had not thought possible.

His presence has already become all-consuming for some. Leading into Saturday’s game, the Turin-based sports newspaper Tuttosport had led its front page with Ronaldo’s face for seven consecutive days.

When this game finally began, though, an unexpected quiet took hold. Was there a hint of nervousness or were we just being reminded that Turin is not Naples or Rome? The tone of this city has always been more reserved than other parts of the peninsula. Juventus’s manager, Massimiliano Allegri, likes to say that moving here transformed him into a “slipper-wearer”.

It was not a cheer but instead a round of whistles that cut through the silence, as Leonardo Bonucci put his foot on the ball: the centre-back’s return to Juventus one year after he deserted them to join Milan has not gone down well with ultras on the Curva Sud. The rest of the stadium was quick to counter with a polite round of applause.

Allegri had sprung his first minor tactical surprise of this season, abandoning the 4-2-3-1 he deployed for the season opener against Chievo in order to move Ronaldo out to the left of attack in a 4-3-3. Hardly a dramatic shift – Juventus had finished with a similar shape in Verona – but nevertheless an acknowledgement that the Portuguese had not integrated seamlessly into existing schemes.

The manager had spoken eloquently about the need for patience before this game, reminding us that “football is a game of connections”, which could only be built through time together on the pitch. Even so, it was hard to escape the sense that Juventus were trying too hard to force the play in Ronaldo’s direction.

After an uneventful first quarter of an hour, the Portuguese moved into the centre, swapping places with Mario Mandzukic in a move that would be repeated several times throughout the course of the game. From here, Ronaldo sowed a little more unease in the Lazio defence, at one point forcing a poor back pass and charging down Thomas Strakosha’s attempt to clear. But the ball bounced harmlessly to safety.

Perhaps his urgency set something off in his teammates as well. Moments later, Federico Bernardeschi retrieved a ball that everyone else seemed to have given up on as it ran out towards the right touchline. The Italian whipped an inviting inswinger towards the middle of the six-yard box, but Ronaldo could not make a decisive touch with his head.

Minutes later it was Miralem Pjanic who opened the scoring with a beautifully taken first-time effort from outside the box. Ronaldo strolled over to congratulate him, yet the celebrations still felt muted. Lazio were very much in the game, carving out opportunities of their own, but somehow the threat of an equaliser still felt secondary to the crowd’s need to see their new No 7 put his name on the scoresheet.

A rising crescendo came down from the stands as Ronaldo hitched his shorts up at the thigh in the customary fashion for a free-kick just after the hour mark, only to be replaced with a groan as his shot flew straight into the wall. He went closer with a turn and dipping strike from the edge of the box but Strakosha pawed it over the bar.

If these were half-chances, then something far more presentable would arrive in the 75th minute. João Cancelo, another summer addition, surged down the right and played a low ball across the area. Ronaldo was arriving right on cue but Strakosha diverted the ball a fraction behind him. Instead of passing into an empty net, the forward succeeded only in clipping the ball with his right boot on to his own left heel.

It was left to Mandzukic to sweep home, sealing a 2-0 win. Ronaldo’s first season with Juventus has begun with a perfect six points from two games. A sense of frustration still lingers, though, as that ketchup refuses to flow.