Before this past weekend, Arsenal had not lost in the Premier League since April. Nine straight league wins had been enough to crown the Gunners as champions at the end of last season and firmly establish them as the team to beat early this season.

Against Brighton on Saturday, though, the team to beat were beaten. Thoroughly.

Arsenal weren’t just pecked by the Seagulls . They were pressed to death by them. Usually so resilient, even in the face of such opposition exuberance, the Premier League champions fell apart on the south coast, losing a match by three goals for the first time in over three years. It was jarring to see Arsenal so out of sorts.

Related: Mikel Arteta agrees contract extension expected to keep him at Arsenal until 2030

Was this simply a Control-Alt-Delete game for Arsenal, or has the manner of the Seagulls’ performance provided a template for others to use? Was Saturday merely a blip that the Gunners will quickly recover from or the first crack in their previously impenetrable armour? Let’s tackle those and some other questions from the Premier League’s big upset before the international break.

The most effective element of Brighton’s performance was their relentless pressing of Arsenal in periods of settled possession. While the Seagulls still had pressing triggers which prompted them to push high up the pitch at certain moments, Fabian Hürzeler also recognised the need to prevent the champions from getting to the edge of the box. They were in Arsenal’s faces for most of the match.

Brighton defensive midfielder Chema Andrés pushed up on to Martin Ødegaard whenever he could, moving Brighton into a man-to-man shape against the ball and limiting the Norwegian whenever he dropped deep. Faced with a four-on-four situation in build-out, Arsenal simply weren’t sharp enough on the ball to get around the press, forcing David Raya to go long more times than he would have liked. From there, Brighton could turn the ball over and attack at speed in the other direction.

This made the match a transition-heavy affair which suited Brighton’s attacking players. Focal point Charalampos Kostoulas was an all-round threat while Pascal Gross, Maxim De Cuyper and Diego Gómez were impactful in open space. Hürzeler’s approach never allowed the game state to shift in Arsenal’s favour. He covered all bases.