Jürgen Klopp’s last dance is being performed by wearying limbs. Liverpool’s injury list continues to grow and if the given reason for Klopp’s departure is his running out of energy, he may also be running out of players. Victory at Brentford kept Liverpool top of the Premier League but only after injuries to important players in Curtis Jones, Darwin Núñez, scorer of an incisive opener, and Diogo Jota, provider for that goal. “As long as we have 11 players we will go for it,” Klopp said after Liverpool had seen out what he described as a “very good game in difficult circumstances.”

Klopp’s squad is stretched to its limits when Manchester City have Erling Haaland and Kevin De Bruyne looking fresh as spring lambs. At least Mohamed Salah, an emergency first-half substitute, was back in harness, supplying the assist for Alexis Mac Allister and then scoring Liverpool’s third, his return hugely timely. On his arrival, he initially looked rusty, including a miss at the start of the second half where he got his feet all tangled. But normal service was swiftly resumed, killing off an opponent his manager declared were “annoying” to face.

Related: Darwin Núñez’s attacking chaos is carrying Liverpool’s title charge | Barney Ronay

Even before those injuries, Thomas Frank might have sensed blood from what resembled a Liverpool Carabao Cup selection, a week ahead of this season’s final. Salah was considered only fit enough for the bench after missing eight matches. Liverpool began shakily and early opportunities arrived plentifully for Brentford, first for Vitaly Janelt then Sergio Reguilón. Neal Maupay, living up to his shot-shy reputation, chose to pass rather than shoot. He did rather better when setting up Ivan Toney but his strike partner fluffed badly, the attempt limping wide. Next, Toney’s free-kick in a promising position was hit almost as softly. Still tamer was Toney shooting straight at Caoimhín Kelleher when sent away for a one-on-one by Maupay. A further first-half chance clattered awry, not especially positive marketing for a prized asset.

Without Ethan Pinnock for the first time in 53 matches – “our best defender,” according to their manager – Frank’s resources were stretched, too: “We haven’t played one game with our first XI.” Last week’s win at Wolves had calmed relegation fears but when Conor Bradley, back from compassionate leave and continuing to look a jewel of a find, burst on to a Luis Díaz flick came the realisation that, whatever the personnel, Liverpool possess real danger. “I’m over the moon about him,” said Klopp of Bradley’s return. “Pretty special.”

On a smaller scale, Frank’s team are going through the similar, necessary, change Liverpool previously made under Klopp, from heavy metal to progressive. This season has seen their novelty value badly fade and this defeat included multiple regrets. Until Núñez struck, Brentford actually looked far likelier scorers. “We were brilliant the first 35 minutes,” said Frank. “On a different day we would have shown the quality of coolness.”

The game turned on a route-one goal that late-1980s Wimbledon would have cherished. Virgil van Dijk launched away a second ball from his own box after a Mark Flekken free-kick. Jota’s nod down found Núñez in space. The lobbed finish was uncharacteristically cool. Liverpool fans have seen the Uruguayan miss far easier chances. “The first goal we have conceded from an offensive set piece in two years,” lamented Frank.

Liverpool’s joy was tempered by Jota almost immediately having to depart with a knee injury so painful the forward was unable to stand. Núñez’s withdrawal at half-time added further to the medical department’s workload, following a first half in which the stats showed Brentford registering just one foul.

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“That Curtis cannot play on tells you something,” said Klopp. “Normally he would carry on at all costs. Diogo looks probably the worst … Darwin felt something.”

Worryingly for Frank, his team’s organisation collapsed after the break. Mac Allister’s goal followed statuesque defending and Salah ought to have been second best to Nathan Collins when Cody Gakpo flicked on a Kelleher kick for another Crazy Gang-style strike. After a couple of questionable decisions from Michael Oliver, the referee had fuelled home fans’ fire, Toney scored, slotting the rebound from Reguilón’s shot with a previously absent precision.

But there was no rousing comeback. Saman Ghoddos’s blunder allowed Díaz to set up Gakpo, completing a comfortable scoreline not reflecting Liverpool’s human cost.