When the question is asked of what has changed about this Liverpool side to turn them from a team of flatterers, not-quites and almost-theres into genuine contenders, two names are often given in response: Alisson and Virgil van Dijk.
That pair, at a cost of nearly £150million, have given Jurgen Klopp's team a resilience, a backbone, the absence of which had previously held them back in fulfilling the potential their ludicrous attacking talents suggested they could reach.
In Mo Salah, Roberto Firmino and Sadio Mane, Liverpool had an attacking trio that rivalled the most devastating in world football. They just did not have the spine to match.
Virgil van Dijk (left) and Alisson are often given as the reason for Liverpool's improvement
The emergence of Fabinho in defensive midfield has also been crucial for Liverpool
Reduced to its most simplistic terms: Liverpool blew teams away, they struggled to grind them down.
Now, they can do both. That is why they are top of the Premier League in one of the greatest title races in history, and it is why they are now in the semi-finals of the Champions League.
But it is not just those two alone who have made a stark difference.
Meanwhile, going about his own business, unperturbed, undistracted by the wilderness around him, a £40m Brazilian adds another gritty dimension to this Liverpool side.
A little over 15 minutes had ticked by at the Estadio do Dragao when Fabinho nicked his toe in to win the ball then, with a swarm of blue-and-white shirts suddenly buzzing around him, he lumped the ball long into the channels. Sadio Mane hustled after it as Liverpool reset their shape. Danger averted.
The Brazilian produced a brilliant piece of play to see off the challenge of Yacine Brahimi
Five minutes later and Fabinho saw Porto winger Yacine Brahimi about to challenge him
