Richard Buxton: Arsenal's new signing David Luiz is their weakest link

David Luiz's overarching problem has always been that he refuses to think like a defender.

Arsenal's summer signing invariably finds himself under the microscope whenever blundering backlines find themselves severely punished.

A 3-1 defeat by Liverpool yesterday morning (Singapore time) became the latest case in point.

Excuses of Luiz needing to bed into new surroundings simply do not wash for a player now in his eighth season in the English Premier League and who just made his 250th appearance.

Unai Emery would not have rushed into a reunion with his former Paris Saint-Germain ally if he had still needed to adapt.

But the north Londoners have previous form for gambling on ageing Chelsea cast-offs.

Petr Cech never vindicated John Terry's assertion that his former teammate would add double figures to their points tally per season.

Luiz's own switch across the English capital was similarly supposed to reinforce the Gunners' rearguard. Current evidence suggests otherwise.

All three goals conceded at Anfield stemmed from a catalogue of errors by the Brazil international.

His lack of authority in marshalling the visitors' defence gifted Joel Matip a free reign to open the scoring in what was, until that point, a fairly even contest.

Shirt-pulling shenanigans, which allowed Mohamed Salah to open his account from the penalty spot, further underline the all-too-familiar flaws in Luiz's defensive make-up.

He was also rendered powerless as the Liverpool forward extended the lead again with a pacy run and finish.

Luiz, however, was a victim of tactical circumstance as much as personal indiscipline.

Had he not been already walking a tightrope with a booking, Salah would not have breezed through.

Likewise if Emery had tailored his side to play to the 32-year-old's strengths, Arsenal may have improved an abject record against their top-six rivals.

Since defeating Manchester City in January 2015, they have taken just eight points from a potential 69 and failed to win in all 23 meetings with their more illustrious peers.

At Anfield alone, they have shipped an alarming 25 goals on their previous seven visits.

Emery and Luiz spent a year together at the Parc des Princes, where the flashbulbs continue to burn far brighter than the spotlight.

Any concerns about the latter were further eroded by the imbalance of Ligue 1 that ensures PSG's annual coronation has become a mere formality.

Yet the warning signs were evident in the French capital, just as they were at Chelsea.

Operating in a flat back four has never sat comfortably with Luiz. His starring role in the EPL title's return to Stamford Bridge in 2016/17 proves that his forte remains as being the kingpin of a three-man defence.

Attempts to deviate from that ultimately end in horror shows like at Anfield.

By default, Luiz assumes the fall-guy status far easier than others, but Emery arguably had set up Arsenal to throw away their 100 per cent start to the season with an approach designed to stop Liverpool steamrolling them as proved the case on his first trip to Merseyside.

It worked initially, with Nicolas Pepe and Pierre-Emerick Aubameyang able to find chinks in the hosts' defence.

Adrian was still struggling to fill the void of Alisson's absence, while Virgil van Dijk finally succumbed to mortality.

No player had managed to dribble their way past Liverpool's imperious centre-back in over 17 months and a half-century of matches until Pepe beat him on a counter- attack.

Van Dijk's standing ensures a relatively tame level of scrutiny for his rare lapse. He will be a driving force in Juergen Klopp's side again vying for the EPL title.

Luiz's preceding reputation, meanwhile, is why Arsenal are not even in the conversation.