Keita leaves Klopp no nearer Henderson answer
The importance of Jordan Henderson to this Liverpool side was glaringly apparent here.
There may be better passers of the ball in the Reds squad, more effective finishers, more creative minds, more imposing tacklers.
Sure, Henderson has impressive measures of each attribute.
But where he truly excels is as a leader, the man who drives the tempo and sets the example from which his team-mates follow.
Liverpool could have done with a bit of that before the break as, despite the early fillip of Gini Wijnaldum's opener, they were disappointingly out of sorts.
The sight of Roberto Firmino twice tracking back to atone for earlier miscues spoke volumes.
Naby Keita, brought into the midfield three, struggled to make any consistent impact and too often lost possession, although he wasn't alone in that regard.
Keita couldn't be faulted for his defensive work – no Liverpool player made more tackles – but it was no surprise when hooked after an hour, another evening when he wasn't quite able to grasp the opportunity when his undoubted guile and imagination was required.
His replacement, Alex Oxlade-Chamberlain, at least offered some urgency and power against an extremely physical West Ham side, the crowd responding to his efforts.
But the first audition to decide who replaces Henderson over the next few weeks left Klopp no nearer discovering the answer. The skipper can't return quick enough.
Alexander-Arnold leads the way
Few Liverpool players reached anywhere near their best level on a night when toil and sheer determination led the way.
But if there was one who bucked that trend, it was Trent Alexander-Arnold.
What quality there was could often be found at the feet of the youngster, whose two assists moved him on to 12 for the season in the Premier League – matching his own record for a defender in the competition.
With 25 assists in the top-flight, only Cesc Fabregas and Wayne Rooney have reached that landmark at a younger age, the right-back still only 21 years and 140 days old. Some company.
Sometimes it's easy to forget that, particularly when his standards dip. Alexander-Arnold is still learning the game.
If the first assist was a trademark peach of a cross from the right, headed in by Gini Wijnaldum, both owed much to his desire to keep the ball alive.
In Henderson's absence, the right-back grasped the initiative, and assumed extra responsibility.
Virgil van Dijk was the captain, but Alexander-Arnold was the inspiration.
Liverpool show they still want it
There was a very unusual feeling for 14 minutes during the second half at Anfield.
For the first time since the closing stages at Aston Villa on November 2, Liverpool were behind in a Premier League game.
With Klopp's side having had the rare experience of defeat last time out in the Champions League clash at Atletico Madrid, the critics were ready to capitalise on, finally, a chink appearing in the Reds' armour.
Were Liverpool losing their way?
Nope. Instead, this was another example of the Reds digging deep and showing sheer determination to get the job done.
Mohamed Salah was a case in point, his touch often off but never chucking in the towel, and that commitment rewarded by Lukasz Fabianski shovelling in his weak effort for the equaliser.
They all count. Salah, with 19 for the season, now has seven goals and two assists in seven games against the Hammers.
And if Alisson Becker was caught out for Issa Diop's opener, he more than atoned with a vital save from substitute Jarrod Bowen in injury time to keep the three points.
West Ham possibly deserved more, with David Moyes still waiting on a first win at Anfield after 16 attempts. This, though, is why Liverpool are the best team in the world – even when they don't look it.