For Mikel Arteta, this was a timely reminder of just how fine the margins can be at the top. With his side leading thanks to Kai Havertz’s sublime lob, the Arsenal manager could have been forgiven for thinking they were on their way to a third comfortable victory in a row to start the new campaign after securing the surprise loan signing of Raheem Sterling from Chelsea on deadline day. Yet four minutes of the second half had been played when disaster struck as Declan Rice was sent off for a bizarre moment when he tangled with Brighton’s Joël Veltman as he tried to take a free-kick. Jõao Pedro went on to equalise for Brighton as they kept pace with Arsenal and maintained their unbeaten record despite both sides having their chances to claim all three points late on. But it was Rice’s second yellow card and then a red – the first of his Premier League career that means he will miss the north London derby after the international break – that proved the game’s turning point. The referee, Chris Kavanagh, left the pitch to boos from the home fans and facing lots of questions from a furious Arteta having failed to keep control of a fiery contest. There had been an extra loud cheer before kick-off when Sterling’s name was announced along with fellow new Arsenal signings Mikel Merino and goalkeeper Neto. Arteta had hoped that Merino, the Spain midfielder, could have been on the bench until he suffered an unfortunate shoulder injury during his first training session on Thursday, but he had to settle for a seat in the stands alongside Sterling, who was not registered in time to feature. Several of Brighton’s new arrivals have also been sidelined, with the Turkey defender Ferdi Kadioglu ruled out after picking up an injury in training on Friday. That meant Jack Hinshelwood continued to deputise at left-back and he needed a pep talk from Fabian Hürzeler after 15 minutes of being run ragged by Bukayo Saka when a crestfallen James Milner had to limp off. With new central midfield signings Matt O’Riley and Mats Wieffer also on the treatment table after joining this summer, Brighton had to turn to substitute Yasin Ayari to fill the void alongside fellow 20-year-old Carlos Baleba – combined age two years more than Milner. The visitors managed to establish their rhythm after the early storm and an attack started by Baleba ended up with Kaoru Mitoma flashing a volley just past the post. But they had no one else to blame but themselves for falling behind seven minutes before the break. Lewis Dunk was far too casual in dealing with a hopeful ball forward and ducked out of the way rather than heading it. Saka sensed his chance, spinning in behind him and then playing in Havertz to execute a brilliant lobbed finish over Bart Verbruggen. Hürzeler’s frustrations boiled over soon after when he was booked for protesting that Rice’s lunge on Veltman should have resulted in a heavier punishment than a yellow card. It then needed Hinshelwood to hack away Rice’s goalbound shot after a lovely flowing move featuring a backheel from Jurrien Timber as Arsenal came out strongly after the break. The England midfielder’s afternoon took a dramatic turn for the worse when he was sent off after being shown a second yellow card. Veltman had been awarded a free-kick but Rice subtly kicked the ball away and was kicked by Veltman at the same time, with Kavanagh ruling that only the Arsenal midfielder deserved a caution for obstruction. The home fans were understandably upset and their mood towards the officials only darkened when Dunk redeemed his mistake by playing a straight ball right through the middle of Arsenal’s defence to Yankuba Minteh. His shot was saved but Pedro gobbled up the rebound – the first goal Arsenal have conceded this season. Arteta’s response was to bring on Riccardo Calafiori and switch to a back five, with Martin Ødegaard just unable to pick out the Italy defender for a chance when he made a lung-bursting run down the left flank. Brighton continued to build the pressure, although Havertz was denied by Verbruggen’s outstretched leg before Saka failed to convert another decent chance on the break. Substitute Georginio Rutter and Baleba blazed over late on after Gabriel had blocked the latter’s shot with his stomach. But Arsenal stood firm and at least had the consolation of a point from a game they had looked destined to win, although Everybody wants to rule the world was an interesting choice of tune from the stadium announcer as Arteta headed down the tunnel in pursuit of an explanation from Kavanagh.