On March 3, the Merseyside derby finished goalless. It had a dual significance: the blow to Liverpool's title prospects proved fatal as Manchester City won their last 14 matches. And, seven-and-a-half months later, it remains the last time Liverpool dropped points.
They go to Old Trafford, scene of another stalemate last season, with 17 consecutive league wins. Another would defeat historic rivals, further the sense of crisis at Manchester United and equal two Premier League records: Chelsea's opening nine victories, the best-ever start, in 2005-06 and City's overall best of 18 straight wins.
It would be an astonishing achievement. It shows how City and Liverpool have raised the bar in recent years, but also that Jurgen Klopp's teams excel in finding ways to win.
It is perhaps surprising they have only six clean sheets in those 17 matches, but they have scored at least twice in 16. It shows how remarkably potent they are. Sadio Mane feels the star of those 17 games, with 13 goals, but Mohamed Salah has nine and Roberto Firmino six.
No one else has more productive full-backs, either: Trent Alexander-Arnold has eight assists in that time and Andy Robertson five.
That feared front three are a reason why Liverpool do not need to dominate for 90 minutes. They can master the early blitz, blowing Norwich away with four goals in the first 45 minutes, or the mid-match assault, scoring three times in 18 minutes against Arsenal. Their training-ground work is reflected in their tally of 35 set-piece goals in 14 months; two brought September's win at Chelsea.
They can overwhelm teams and narrowly overcome them, surge to victories and grind them out. Resolve and character account for three triumphs after they trailed. Their formidable fitness, all the more impressive because of their European commitments, is apparent in the five times they have turned a draw into a win in the last 11 minutes, including the 95th-minute decider against Leicester two weeks ago.
While Klopp prefers the consistency that comes from a core, Liverpool have had enough strength in depth to get vital goals from substitutes: Jordan Henderson at Southampton last season, then Divock Origi at Newcastle.
They have shown the resourcefulness to cope with setbacks. They have negotiated two months without Alisson, who may return on Sunday (Oct 20). Injuries have given Virgil van Dijk different centre-back partners. They won without Firmino in May.
Luck helps, too: think of the error by Sheffield United's Dean Henderson for Gini Wijnaldum's decider at Bramall Lane. But the fixture list is the other contributor. Only six of their 17 opponents finished in last season's top 12. Liverpool have been ruthless in disposing of the relative minnows. Far as United have fallen, they should still be among the tougher opponents for men chasing records.