For an hour, Dean Smith will have enjoyed the Anfield serenity. Then he looked to his right, saw the cavalry preparing to charge and left Merseyside as pointless as the previous 24 Premier League visitors.
The Aston Villa manager could only curse Liverpool's quality from the substitutes' bench as Roberto Firmino, Jordan Henderson and Gini Wijnaldum preserved the champions' 100 per cent home record, transforming a meandering game into something more worthy of Liverpool's historic season.
Would Jurgen Klopp have made a treble change in a world without five permitted substitutes? We can only theorise, but Smith had cause to validate his complaints that the relaxing of rules since the restart may have directly impacted on the result. "Definitely. I said that when the rule was put forward, I think by Chelsea," said Smith.
"We do not need rule changes in the season. It was always going to benefit bigger and better squads.
"I don't thank Jurgen for sending the big guns. They upped the quality with three players who would usually be starting."
Klopp might argue the visitors had only themselves to blame for failing to make hay during his side's ponderous period, during which Pepe Reina, preferred to Orjan Nyland, had so little to occupy him he could have been forgiven for re-imagining some of his memorable European experiences in this venue.
Within 11 minutes of the switch, Liverpool were ahead, immediately reacquainting themselves with pace and intensity. Naby Keita played in Sadio Mane, before another substitute, promising teenager Curtis Jones, doubled the lead in injury-time. Liverpool's late excellence is reassuring and paradoxically a cause for concern for Klopp if he is seeking evidence a quiet summer in the transfer market will not unduly damage a title defence.
It still feels indecently early to be talking about that, especially since Liverpool have not yet seen the red ribbons on the Premier League trophy.
Nevertheless, you can't complain about being judged to the highest standards when you are the one who set them, Klopp and his players expressing their determination to ensure this title is the first of many.
Only when the attacking trio of Firmino, Mane and Mo Salah reformed did Liverpool find their mojo. Even when accounting for the understandable lack of jeopardy in their remaining games, it is not the first time that has been written when Klopp has been tempted to tinker. The drop in level is too extreme when one is rested or injured.
With Klopp planning another prudent summer - this time through financial compulsion more than necessity - there is an onus on the back-up squad to drive on.
Many have been barely needed in this title campaign, Divock Origi the go-to man from the bench and during Merseyside derbies, Naby Keita rotating between encouraging and injured, Alex Oxlade-Chamberlain given the time since his long-term absence to make himself a permanent starter rather than deputy.
At the moment, it is Keita who looks next in line behind the central three and James Milner.
"Naby is a top player and he was really good and helped us a lot, not only with the goal. It was an example of how good he could be," said Klopp. Given his instant impact, Jones will be pushing hard at the start of next season, too, the youngster celebrating signing a new deal with deflected strike after being teed up by Salah.
The worries of those who want Liverpool to strengthen are not based on Klopp's favoured line-up being fit and available. It is what happens if too many, especially in the famed front three, are not.
Since assuming heroic status in the Champions League last season, it is fair to say Origi has not been battering down Klopp's door demanding a starting place.
His most regular cameos might best be described as more of a gentle tapping at the window.
Nothing will impact Origi's Anfield legacy. When you write your legend with Merseyside derby goals, a matchwinning contribution to a European Cup semi-final, and the killer goal in the final itself, you get a free pass forever. There are feasts for the Belgian striker to dine out on. That does mean he and his manager should not be greedy for more.
© Daily Telegraph, London