The intense spotlight that has been trained on one elite Liverpool icon turned to another on Anfield's most recent frustrating night.
The Egyptian forward has faced examination for his poor form this season - and was consigned to the bench for the second successive Premier League game as the Black Cats arrived on Wednesday.
But it was skipper Virgil van Dijk, a exceptional defensive rock as Liverpool have collected the complete set of major prizes, whose dip in performance became the focus during the 1-1 draw.
Van Dijk, 34, and Salah, 33, both agreed to new lucrative two-year deals in the summer, with not one Liverpool concern voiced at the notion of handing contracts to a seasoned pair much nearer to the end of their careers than the start.
In fact, it was a reason for joy - but now there is no avoiding the harsh truth that performance has dipped alarmingly for both.
Liverpool have been susceptible in defence ever since boss Arne Slot and the club's transfer committee undertook a £450m summer overhaul that has still to demonstrate anything like a good return.
At the same time, Van Dijk has started to forfeit the aura of invulnerability he has held since his £75m switch from Southampton in January 2018.
Van Dijk has faced additional challenges by fellow defender Ibrahima Konate's dramatic dip, along with Milos Kerkez not finding his feet at left-back. But the esteemed defender has also had significant difficulties, as proved by his desperate handball that conceded a penalty in the heavyweight Champions League loss to PSV Eindhoven at Anfield.
It was captured in the 67th minute on Wednesday when Chemsdine Talbi gave Sunderland a merited lead, Van Dijk losing possession before retreating and turning away on a 25-yard shot that struck him and looped out of the reach of goalkeeper Alisson.
For a defender of such unquestionable quality, Van Dijk has an unusual habit of turning his back on the ball, sometimes to Liverpool's cost.
Misfortune at the finale, yes, but it was a situation Van Dijk provoked with his uncharacteristic failure to act decisively, Sunderland's Talbi taking advantage.
"Van Dijk surrenders possession and then he just retreats. It's the mistake. He needs to go to the ball. Him not making the decision means that no one else knows what to do."
"Virgil Van Dijk last season was impeccable. Every game he was commanding, but right now he's erring and hesitating."
As with Salah, a player of Van Dijk's stature must not be dismissed after claiming two Premier Leagues, the Champions League, the FA Cup and two EFL Cups in a illustrious Liverpool career.
He has, though, looked a faded version of his usual imperious self this season, with the lowest recovery numbers per game during his Liverpool career, while tackles and interceptions are also down on last season.
And, while leadership should not be Van Dijk's preserve alone in a Liverpool team brimming with experience, it was lacking here. No-one was rousing a team that once again looked bewildered to take control by the scruff of the neck.
Van Dijk's subpar showing, which ended with him being used as the emergency option of acting as an emergency striker, was indicative of a deeply underwhelming Liverpool performance - which made Sunday's win at West Ham seem like the outlier rather than the rule.
Slot persisted with the side that stopped a run of nine losses in 12 games at London Stadium, Salah once more starting on the sidelines.
The Egyptian was introduced at the start of the second half as the Kop looked to him for inspiration. It was not forthcoming, with £125m Alexander Isak also quiet after scoring his first with his first league goal for Liverpool on Sunday.
Slot would have been under increased scrutiny had Florian Wirtz's 81st-minute shot not been turned in off Nordi Mukiele to set up what Liverpool hoped would be a grandstand finish.
A late scare came - but at the other end. Liverpool were only spared embarrassment in stoppage time when Federico Chiesa's excellent defensive sprint allowed him to turn Sunderland substitute Wilson Isidor's shot off the line after he had beaten keeper Alisson.
Slot and his underperforming defending champions ultimately had to accept the point knowing it could have been worse, with Alisson lucky to turn Trai Hume's shot onto the bar in the first half before Omar Alderete headed against the post after the interval.
Liverpool were slow, ponderous and lacking in ideas. Even the customary late surge after the equaliser carried little conviction. Showings like this are the reason their title defence has fallen apart.
But huge credit for the Reds' struggles on Wednesday must be given to Sunderland, who are being seeing the results for a summer of notable ambition in the transfer market, coupled with the excellent coaching of Regis le Bris.
The Black Cats were adventurous, assured and a genuine threat.
Sunderland are now sixth in the Premier League with 23 points. It is telling of the manner in which they have grown into life in the Premier League that they will be unhappy they left Anfield without adding two more to their tally.
For Slot and Liverpool, it is time for reflection.
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