[ad_pod ]There is a screen grab that often does the rounds whenever a defensive mistake occurs at Arsenal. Funnily enough, that happens to be on a regular occasion.That image, however, is one that shows Per Mertesacker and Laurent Koscielny's record alongside each other at the Gunners.

At one stage during the 2013/14 season, the pairing were unbeaten when completing 90 minutes next to each other. They'd played 27 matches and conceded just 0.5 goals per game, a total that saw them keep 16 clean sheets in that time.

Like Unai Emery's arrival after Arsene Wenger, you don't always know what you're going to miss until it's gone.

Mertesacker was never a pillar of solidity and a reckless challenge on Diego Costa a few years after those stats came about sums that up.

Koscielny, though, was formerly a club captain and arguably one of their most consistent defenders.

During his time in the capital, he only dipped below an average match rating for a whole season of 7, according to WhoScored, on one occasion - that happened to be his last term.

That was during a season where the Frenchman returned from a horrendous Achilles problem that ruled him out of the World Cup.

Those two defenders are now in the past and even if they don't rank up alongside some of the great partnerships the Gunners have produced, they were comfortably better than what they have now.

The new defensive partnership has seen the rather comical David Luiz line up next to the bad-tempered Sokratis.

Both of them are north of 30 years of age but have so far produced glaring schoolboy mistakes. Should we really be surprised? Not really. This is Arsenal, of course.

Defensive errors seem entwined with the club - you only need to ask Shkodran Mustafi that. He has made countless in the past, whether that be pushing Harry Kane in the north London derby or allowing Wilfried Zaha to steal in against Crystal Palace. Howlers seem to follow him.

But even with the German out of the team, Arsenal's defence is still a catastrophic mess and it's now rubbing off on Sokratis.

The Greek somehow fell below Mustafi in terms of average match ratings last term but that doesn't tell the full story. The key stat is the number of errors leading to a goal.

Arsenal's enigmatic number 20 has made three during his time in the Premier League while their number five has only made one.

That one has come this season and it's only since being included next to Luiz that things have rather fallen apart for the former Dortmund man.

The Brazilian has conceded two penalties and Sokratis has arguably been at fault for two goals too.

He strangely went up for a header alongside Granit Xhaka which then culminated in Spurs' opening goal in the derby and then his lacklustre pass out from the back against Watford led to another ball finding the back of the net.

It's a sorry tale but one that rather sums up the Islington club. When it comes to defending they can't do it consistently, and at the moment it doesn't appear as though it matters who is in charge.

The errors are so basic that it's almost dumbfounding they can even make them in the first place.

But that is the nature of Arsenal. Errors occur and simply keep happening.

Sokratis has never been a defender to shy away from a challenge, claiming 12 yellow cards last term, but the centre-back seems to have lost his head since playing next to Luiz.

What's indicative of that is that the Gunners' only clean sheet in 2019/20 came when he was playing next to Calum Chambers at Newcastle. The pair regularly played in defence together throughout pre-season so it's bizarre they've been split up.

The 31-year-old's numbers are down from last season too, something that clearly hasn't helped Arsenal's cause.

He's made fewer tackles, interceptions and clearances in the Premier League per game and is currently on an average match rating of 6.55 despite having more defending to do. Arsenal conceded 31 shots when they took on the Hornets - not a pretty sight.

Luiz, on the other hand, sits on a 6.37 in the top-flight. Blatantly, it needs to get better.

That being said, the reintroduction of Rob Holding should definitely help.

The central defender has been out since rupturing his ACL against Manchester United last campaign but he has a big future ahead of him. This is a player who Emery spoke about when considering an English captain in pre-season.

His return is timely and it may just be the catalyst Sokratis needs to improve - that's if he isn't dropped for the Englishman.