Arsenal’s 3-2 defeat to Borussia Dortmund in pre-season may not be a major concern in itself, but it highlighted an area Mikel Arteta’s side cannot afford to ignore before the new Premier League season begins.

With their World Cup contingent finally returning to training, Arsenal will soon look far more like the side that won the title last season. Declan Rice, David Raya, Eberechi Eze and Martin Zubimendi are among those set to join up with the squad, while the return of William Saliba remains some way off.

That, combined with Jurrien Timber’s ongoing absence, could make defensive depth Arsenal’s biggest remaining transfer priority.

Dortmund expose Arsenal’s defensive weakness

Arsenal conceded six goals across their last two pre-season matches, although there is little reason to panic over those results.

Pre-season defeats rarely tell the full story, and Arsenal themselves lost 3-2 to Villarreal last summer before going on to enjoy a successful campaign.

However, Sunday’s defeat to Dortmund exposed a more specific problem.

Arsenal looked vulnerable through the middle of the pitch, with Myles Lewis-Skelly operating as the deepest midfielder and two more advanced No.8s ahead of him.

Dortmund repeatedly found space to attack, particularly when Riccardo Calafiori moved away from his defensive position.

The absence of Rice and Saliba was particularly noticeable. Arsenal can afford to play aggressively when those players are available to cover spaces behind the midfield, but the current squad does not offer the same security.

The return of Rice and Raya should immediately improve the situation, but there is still a concern further back.

Saliba and Timber leave Arsenal short

The biggest issue for Arteta is the availability of his defenders.

Saliba is expected to be out for months with a back injury, while Timber is still weeks away from returning.

That leaves Arsenal with limited options if another injury occurs.

Gabriel has not looked at his best during pre-season, while Cristhian Mosquera has been required to move into central defence in Saliba’s absence.

Ben White is therefore particularly important to Arsenal’s defensive structure.

The 28-year-old is only just returning from an MCL injury, making his availability another potential concern.

And the situation becomes even more problematic at right-back.

With Timber unavailable and White needed to cover the position, Arsenal have had to rely on teenage defender Theo Julienne for depth after Louis Copley suffered an ACL injury.

For a club attempting to defend the Premier League title, that is a significant vulnerability.

Arsenal need versatility, but right-back may be the priority

Arsenal are already understood to be looking at versatile defensive options.

Ezri Konsa has been linked with the club, although Aston Villa’s reported £60 million valuation is above Arsenal’s assessment of the player.

Cristian Romero has also emerged as a potential target.

A centre-back would certainly provide Arteta with additional depth, but Arsenal’s bigger problem may actually be at right-back.

The Gunners already have several players capable of operating centrally.

Mosquera can continue developing in the position, White can move across when necessary, Timber can also play centrally once fit and Piero Hincapie provides another option.

Right-back is different.

An injury to White would leave Arsenal facing a significant reshuffle at a time when Timber will need to be carefully managed following his return.

The Vinicius question

Much of the attention surrounding Arsenal’s transfer plans has focused on strengthening their attack, including their interest in Vinicius Jr.

But the Dortmund defeat should force the club to consider whether defensive depth is actually the more pressing need.

Arsenal are recruiting from a position of strength after winning the Premier League last season. They therefore do not need to overhaul the squad.

They need to make sure that injuries do not undermine the quality of the starting XI.

The return of Rice, Raya and the rest of Arsenal’s World Cup contingent will solve several of the problems seen in pre-season.

But Saliba’s absence cannot be solved internally as easily.

A defender could be Arsenal’s final major piece

Arsenal have the numbers to cope with Saliba’s absence in central defence, but their lack of natural right-back cover is much harder to overlook.

The club cannot assume White and Timber will remain available for the entire season, particularly given their recent injury histories.

That makes adding a defender capable of covering right-back and centre-back an attractive solution.

It would give Arteta greater flexibility, protect against further injuries and reduce the need for disruptive positional changes.

The Dortmund defeat should therefore not be viewed as evidence that Arsenal are in crisis.

Instead, it provided a useful warning before the season begins.

With the Community Shield approaching and the Premier League campaign around the corner, Arsenal’s priority should arguably be clear: **strengthen the defence before spending heavily on another attacking option.**

If Arteta gets that depth right, Sunday’s 3-2 defeat to Dortmund will quickly become little more than another pre-season footnote.