There are few people on this planet better qualified to judge a Liverpool centre-forward than Ian Rush. The man scored 346 goals for the club — a record that still stands, and probably always will — so when he offers a verdict on Alexander Isak, it is worth sitting up and paying attention.

And his message heading into the new season is a simple one. Isak is coming, he is ready, and those who wrote him off during a torturous first year at Anfield might want to think again.

"I'm hoping Isak comes back a new player," Rush told the BBC. "He'll be ready. He doesn't need a pre-season. He's got over his injuries and he's played for Sweden at the World Cup. I think he'll be coming back looking to prove a thing or two to other people."

Strong words. And when you consider everything Isak has been through since that £125 million move from Newcastle — still the most expensive transfer in Premier League history — they feel entirely justified.

The story of Isak's arrival at Liverpool was hardly the smoothest. The switch was drawn out and acrimonious, with the forward going on strike to force the move through. By the time he actually pulled on a red shirt, he had missed pre-season entirely. Getting up to speed under those circumstances, in a Liverpool side that was struggling to find its own rhythm, was always going to take time. Isak looked exactly like what he was — a player trying to settle into a new club, a new system, and a new city, all at the same time, without the benefit of a proper pre-season to bed himself in.

Just when things were beginning to click, fate intervened in the cruellest possible way. In December, in the act of scoring in a win at Tottenham Hotspur, the 26-year-old suffered a broken leg. It was the kind of moment that makes you wince just thinking about it. A player finally finding his feet, finally contributing, and then — gone. The rest of the season spent watching from the sidelines.

Isak still has not completed a full 90 minutes in a Liverpool shirt. That is a remarkable stat for a player of his calibre and cost, though the circumstances behind it make it far more understandable than damning. The question heading into the new campaign has always been straightforward: what do Liverpool actually get when they have a fully fit, fully settled Alexander Isak?

Rush clearly believes the answer is something very special. And the signs from the summer are genuinely encouraging. Isak returned to international duty with Sweden at the World Cup and by all accounts performed well enough to demonstrate that the leg break has not left any lasting mark. He arrives for Liverpool's pre-season tour of the United States in the coming days, with friendlies against Wrexham in New York and Leeds United in Chicago potentially offering his first competitive minutes in a long time.

The timing is interesting. Liverpool's new head coach Andoni Iraola is still in the process of putting his stamp on the squad, and in many ways Isak represents an almost entirely unknown quantity. Iraola has had precious little opportunity to actually work with his most expensive asset in any meaningful way. In that sense, Rush's framing of it is spot on — this is almost like a new signing arriving at the club.

The difference, of course, is that Isak does not need to settle into the Premier League. He does not need to adjust to the pace or the physicality or the demands of playing at Anfield in front of the Kop. He has already done all of that, however briefly. He knows the place, knows the expectation, and knows that he has something to prove. That last part might be the most important factor of all.

Players with a point to make can be dangerous things. A striker of Isak's quality, carrying a chip on his shoulder after a debut season that fell spectacularly short of what everyone — including himself — would have hoped for, is a genuinely exciting prospect.

Rush has seen enough great Liverpool number nines to know one when he spots one. If he reckons Isak is about to show everyone what he is really about, Iraola would do well to get him on the pitch and find out just how right he is.