Looking back, it should have been obvious. Liverpool had picked up 196 points in two near flawless seasons, winning their first title in 30 years and becoming champions of Europe and the world along the way. It is impossible to do that without every aspect of the team functioning close to perfection.
The excitement that accompanied Thiago Alcantara's arrival at Anfield focused on what he could add to the side. It was hoped that this playmaker extraordinaire, this master manipulator of the ball, could add a new dimension to Jurgen Klopp's attacking play. But perhaps there should have been greater awareness of what Liverpool would lose too.
The midfield was never a problem, it was the engine. The ceaseless work of Fabinho, Jordan Henderson and Georginio Wijnaldum sustained the attacks, recycling possession for the full-backs to raid forward again and again. When Trent Alexander-Arnold and Andrew Robertson pushed on, they would cover. The creativity was outsourced but it was never lacking.
Thiago should not become the scapegoat for the team's struggles since then. There have been too many other variables, too many moving parts in this once well-oiled machine, to identify just one reason for the slump that leaves Liverpool more concerned about maintaining their top-four position than successfully defending the Premier League title.
But the bald statistics tell a tale. After going almost four years without losing a league game at Anfield, they have been beaten there three times in a row. Thiago has started the lot. Liverpool have won only two of the nine games in which he has started and that does not include the 3-1 defeat at Leicester on Saturday when he came on in the 17th minute.
Thiago has struggled badly without the ball, being labelled a "liability defensively" by Jamie Carragher. This Liverpool team with Thiago at the heart of its midfield has just not worked.
The familiar touches of quality have still been evident. Those blind passes, frequently fizzed into the feet of the forwards, have encouraged Liverpool to break the defensive lines and make it a little unfair that he should be accused of slowing down attacks. He retains the ball, keeps it moving, spreads the play wide, and is always searching for the correct pass.
But there is an awareness now that his presence also weakens Liverpool defensively. He has been unable to protect the defence at a time when the defence has ached for protection.
Approaching 30, he has looked like a player struggling with the pace of the game around him when the opposition are on the transition. He has become a serial fouler.
Stopping counter-attacks is nothing new for Thiago. There was an expectation that he would perform that function at Bayern Munich too. But his team were able to control that rather better in the Bundesliga. At Liverpool, he has been left exposed far too often.
It is evident in the numbers that show Thiago is fouling more than ever before, committing almost double the number of offences that he had averaged in his final four years at Bayern.
This unwelcome habit almost resulted in Liverpool conceding a penalty at Leicester when he needlessly dangled out a leg on the edge of the box. The decision was overturned on review but the free-kick still found its way past Alisson and into the net, turning the game.
The impression of Thiago is of a man on the edge of his capabilities, playing at his physical limit in trying to contain opponents who are conspicuously more dynamic than him.
He has always been a tackler. He attempted more than three of them per 90 minutes in each of his last five seasons at Bayern, attempting 4.7 per 90 minutes during the 2015/16 Bundesliga campaign - even more than his 4.5 tackles per 90 minutes as a Liverpool player.
But there is a significant difference lurking in these numbers. The success rate of Thiago's attempted tackles is far, far lower at Liverpool than it had ever been at Bayern Munich. Perhaps worryingly, his tackling success has been declining year after year.
How much of this can be explained by Liverpool's system not functioning as before and how much is a consequence of Thiago's lack of physicality contributing to the loss of control?
Certainly, the presence of Virgil van Dijk, with whom Thiago has spent only 56 minutes on the pitch, would have helped Liverpool maintain a higher line without it appearing so fraught with danger. Thiago would not have looked so isolated in midfield as a result.
Their 56 minutes together included the second half against Chelsea at Stamford Bridge when Liverpool scored twice without a reply and the first 11 minutes of the Merseyside derby at Goodison Park when they took an early lead before Van Dijk went off injured.
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Able to focus on his undoubted strengths with the ball at his feet, Thiago clearly still adds something to this Liverpool team and there can be hope that when normal service is resumed then the benefits of his influence on the team will be more keenly felt.
But right now there is a growing appreciation that even a craftsman like Thiago, a midfield maestro, has, by his mere introduction, altered the delicate ecosystem at Liverpool.
The job of a Liverpool midfielder remains to provide some of that cover when sweeping in behind Alexander-Arnold and Robertson. But while that came naturally to Henderson, it has been awkward for Thiago. He does not have the skill-set required for that role.
The Liverpool midfield, while not as celebrated as the goalkeeper and defenders behind it or the attackers in front of it, was a fundamental reason for the success of the side.
Looking back, it should have been obvious.