After Saints missed a couple of chances, the Reds went in front on the stroke of half-time when Mane curled a superb effort into the top corner against his former club.
Firmino added a second 19 minutes from time before ex-Liverpool striker Danny Ings profited from a mistake by Adrian, who was fit enough to start despite an ankle issue, to set up a nervy finish.
Here are three talking points from St Mary’s.
INDIVIDUAL QUALITY MATTERS
If there is one trait Liverpool have developed over the last 12 months, it’s that they are merciless.
Take the game as a whole, and Jurgen Klopp’s men did not merit three points at St Mary’s.
The difference was in the details. Southampton in the first half were far better as Liverpool’s exhausting exploits on Wednesday in the Super Cup extended to Saturday.
A lethargy infected the Reds and Southampton needed no invitation to feed off their inertia, charging high up the pitch and forcing the visitor’s into imprecision on the ball.
For large parts of the opening half, Liverpool struggled to get out of their own half as the front three was left completely isolated.
But during this period of dominance, Southampton did not have any tangible success. Maya Yoshida was denied by Adrian’s superb close-range stop after heading James Ward-Prowse’s delicious corner.
There was panic in the box when Ryan Bertrand’s dangerous low cross pinged across the area as Adrian feathered the ball into a swarm of Southampton attackers, while striker Che Adams also had a sight of goal only to head over.
All that was missing was a touch of quality and Liverpool have exactly that. It takes only a moment for it to be effective.
In tight space on the left, a series of one-touch passes between Andy Robertson, James Milner and Mane opened Southampton up and the Senegalese shifted inside to unleash a gorgeous strike into the far corner.
It was a ruthless passage of play right before half-time. After the break, Southampton’s press lost steam and as their energy levels dropped, the opportunity to prosper narrowed.
Liverpool went on the hunt and Firmino’s quality also told, his drilled effort killing the game off. Or so they thought…
ADRIAN’S ROCKY MOMENT
Jurgen Klopp was hailing back-up goalkeeper Adrian’s “Rocky moment” after his Super Cup heroics.
On Saturday, there were plenty more rocky moments, only this time, the Spaniard’s new colleagues were left screaming in pure anger.
Naturally, the focus of their vex will zero in on the howler which let Southampton back into the game. It’s a scenario which has played out hundreds of times with Alisson, the defender in possession finding no route forward and turning to start again from the keeper. Virgil van Dijk calmly played it back to Adrian from the left, the goalkeeper was unrushed and effortlessly passed it into his own net off Ings.
It wasn’t the first sedate moment either with Adrian very fortunate in the first-half when Ward-Prowse mirrored Ings only for the ball to go harmlessly out for a goalkick.
His distribution was generally quite poor, a passing accuracy of 75.9 percent more than five percent down on Alisson’s average in 2018/19.
However, the Brazilian too had his own faux pas early on last season against Leicester and perhaps Adrian should be afforded the same grace he was, especially considering the mistake didn’t effect the points haul.
OX IS ACTUALLY LIKE A NEW SIGNING
Liverpool fans spent the summer in a meltdown and it had nothing to do with the temperature outside.
Indeed, the club’s inactivity in the transfer window left many anxious going into the new season and that wasn’t aided by Klopp labelling Alex Oxalde-Chamberlain and Adam Lallana as “like new signings”.
Although supporters’ ire can be forgiven in regards to the latter, in Oxlade-Chamberlain’s case it’s a legitimate assessment.
The 26-year-old was excellent on Saturday. Emboldened in the middle three after an unsuccessful outing in the front trio on Wednesday, the England international gave Liverpool a drive through the middle which has been missed.
In the first minute, he bounded through the centre with bowling-ball-like qualities, carrying possession to the edge of Southampton’s box and slipping in Trent Alexander-Arnold on the right to create an opening.
There was a superb piece of combination play with Salah which ended with a sumptuous first-time cross from the right byline.
He created chances and stopped them too, covering for Alexander-Arnold after the right-back was caught out high up the opposite end with Oxlade-Chamberlain walling in Nathan Redmond to shut down an avenue to goal.
The former Arsenal man was explosive in pockets and tidy with his passing as well, a total contrast to the rest of Liverpool’s midfield.
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