The 23-year-old, introduced as a second-half substitute, combined superbly with fellow reserve Xherdan Shaqiri to secure victory on an onerous night for the hosts.
Given the injuries and the flood of fixtures, it was not going to be easy, pretty or particularly enjoyable for and from Liverpool.
But the champions seemed to have time-travelled, back to a period where they were stumped by deep defences: too slow, not enough aggression, too many touches and predictably playing in front of the opposition, all while looking shaky at the back.
The game had just hit double digits in minutes when Liverpool’s passiveness out of possession was punished.
Jarrod Bowen was afforded time and space in the centre circle to feed Aaron Cresswell on the left, who then supplied Arthur Masuaku.
Curtis Jones continued the trend of not putting pressure on the ball from Liverpool by failing to stop the cross.
Joe Gomez’s attempt to clear the delivery was weak and only reached as far as Pablo Fornals, who controlled and beat Alisson inside his near post.
The lead allowed West Ham, without injured talisman Michail Antonio, to get comfortable in their obstructive organisation as Liverpool did not do anything to disrupt them.
Jurgen Klopp’s side were not creating much of note, so were thankful to Masuaku for clipping Salah’s Achilles from behind without making any contact with the ball in the box.
The Egyptian struck his penalty straight down the middle and retrieving the ball was the only real energy West Ham goalkeeper Lukasz Fabianski expended in the first half.
The second 45 meandered on until Shaqiri and Jota were introduced for Jones and Roberto Firmino, making Liverpool more direct.
The Portugal international was immediately in the spotlight as Klopp’s side contended with another VAR decision they will not be best pleased with.
Sadio Mane had a shot parried by Fabianski and slid in for the loose ball, which broke for Liverpool’s new signing to convert.
A lengthy check took place and the Senegalese’s boot had clipped the keeper. The referee, Kevin Friend, consulted his monitor and disallowed the goal.
But that wasn’t enough to thwart Jota from becoming the first Liverpool player to score in each of their opening three home games in the competition since Luis Garcia in October 2004.
Shaqiri delivered an intelligent ball, through a sea of defenders trying to get a block in, down the inside left channel to free Jota.
He slammed it into the bottom left to keep his run intact and keep Liverpool top of the table.
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