Barcelona’s 5-2 victory over Rayo Vallecano may have delighted supporters, but the result also exposed a problem that could become dangerous against stronger opponents.

Hansi Flick’s team scored five goals and moved to the top of LaLiga, with Raphinha and Lamine Yamal both scoring twice. However, Barcelona also conceded twice after Rayo repeatedly found ways through their defence.

The attacking performance was spectacular. Barcelona responded immediately after conceding early and eventually overwhelmed Rayo with their technical quality.

Yamal’s performance was particularly impressive, reinforcing his status as one of the most exciting young players in world football.

But the defensive issues cannot be ignored.

Barcelona allowed Rayo back into the match after building a 3-1 advantage. At 3-2, the visitors were suddenly within one goal of an equaliser before Raphinha restored Barcelona’s two-goal advantage.

That pattern may not be so easily corrected against elite Champions League opponents.

Flick will therefore have a difficult balancing act. Barcelona’s attacking philosophy is built around possession, pressing and creating large numbers of chances, but the team must also prevent opponents from exploiting spaces behind the defence.

The good news is that Barcelona have nine points from their first three league matches.

The warning is that their next major opponent may not be as forgiving as Rayo.

For now, the champions are winning — but whether they can defend well enough to dominate Europe remains a major question.