Maybe it shouldn't have been so shocking that the side capable of halting Arsenal's championship push would be captained by their former skipper, their former captain. The substitute Brobbey netted an stoppage-time leveling goal after late strikes from Saka and Trossard had put the visitors in the lead following a early goal from the home side skipper Dan Ballard.
Proved to be a rocky match for the English top division leaders, but Arsenal have a seven point advantage over City, who are at home Liverpool on the weekend, and the hosts, though the Blues could cut the lead to six points in the weekend's evening fixture.
The Swiss international – who left the Emirates Stadium in last year seeking what he described as a fresh opportunity – has been outstanding in the newly promoted team's engine room this campaign after joining from the German club, but the veteran's performances on Sunderland's home turf will not have surprised Gunners fans. The Swiss international revived his Gunners stint under Arteta, who was reluctant to see him leave.
Sunderland went into the match with nothing to lose after making the strongest opening to a top-flight season by a newly promoted club over 10 games since Hull City in the 2008/09 season. A deflected strike from Xhaka against the Toffees on earlier in the week had boosted them up to fourth place, a standing not many home supporters would have envisaged before a ball was kicked given that their side had spent almost a decade outside the top flight.
The player's experience, largely gained during his lengthy spell at the Emirates, and leadership have assisted the team rapidly adapt to Premier League football. He seemed to revel in the intensity of the contest.
Arteta, again without Gabriel Jesus, Martin Ødegaard, Kai Havertz, Noni Madueke, Viktor Gyökeres and Martinelli, had an early concern when Mikel Merino, playing up front after scoring a brace in Tuesday night's three-nil Champions League win at Prague, was struck by an elbow from the defender as he attacked a ball into the home box. Merino was fit to continue.
Eberechi Eze nearly took advantage of an error from Le Fée, who lost the ball on the edge of the box, but the shot soared over the bar.
Isidor fired off target at the opposite side before another lengthy break after a clash of heads between Le Fée and Timber, who had to continue with a bandaged head.
A tougher blow was to follow for stunned the visitors. Sunderland launched a set-piece into the Arsenal area and the captain held off Rice to lash the ball past David Raya after it was cleared. It was the opening strike Arsenal had conceded since their last visit to the North East in September's end, when they had underlined their championship potential with a late win over Newcastle.
Arsenal had maintained a club-record eight successive clean sheets in all competitions since Nick Woltemade's goal against them at Newcastle's ground.
Sunderland ensured that it was a further uncomfortable outing to the region for Arsenal, who found themselves under pressure for spells after the interval.
They required a instance of quality, and it came in the 54th minute. Rice took the ball off his opponent and a flowing move involving Eze and the striker ended with the forward beating Roefs at his near post.
The visitors pushed for a next score and the coach made three changes to his offense – he sent on Brobbey, Chemsdine Talbi and Simon Adingra – midway through the final period.
A further example of quality was not long in coming. Arsenal moved the play from one flank to the other, and Trossard, just outside the area, created enough room to fire a right-foot shot into the top corner.
The keeper had to be sharp in the final stages as Sunderland pressed for a second goal, but could not stop an spectacular finish from the substitute after the ball was headed into the penalty area. The strike was met by a deafening cheer.
Fittingly the defender – like Xhaka a former Arsenal player, this one coming through Arsenal's academy – had the last word with a flying block at the feet of the attacker in the match's final moment.