It perhaps wasn't so shocking that the side able to slow Arsenal's title charge would be captained by Granit Xhaka, their former captain. The substitute Brobbey netted an injury-time equaliser after late goals from Bukayo Saka and Trossard had given Arsenal ahead following a early goal from Sunderland skipper Ballard.
Proved to be a difficult night for the Premier League pace-setters, but the Gunners maintain a seven-point lead over Manchester City, who are at home Liverpool on Sunday, and the hosts, though the Blues could cut the lead to six points in the weekend's later game.
The Swiss international â who departed the Arsenal's home in 2023 seeking what he described as a new challenge â has been outstanding in the promoted side's midfield this season after signing from the German club, but the 33-year-old's form on Sunderland's home turf will not have shocked Gunners supporters. The Swiss international revived his Gunners stint under Arteta, who did not want to lose him.
The Black Cats went into the match with nothing to lose after achieving the best start to a Premier League campaign by a promoted side over 10 games since Hull in the 2008-09 term. A redirected effort from Xhaka against Everton on earlier in the week had lifted Sunderland up to fourth place, a position few local fans would have envisaged before a match began given that their side had spent almost a decade away from the Premier League.
Xhaka's expertise, largely earned during his seven years at the Emirates, and leadership have helped the squad rapidly adapt to Premier League soccer. He appeared to thrive in the physicality of the encounter.
Arteta, once more without Jesus, Martin Ădegaard, Havertz, Noni Madueke, Gyökeres and Martinelli, had an early concern when Merino, leading the line after scoring a brace in Tuesday night's 3-0 Champions League win at Prague, was caught by an elbow from Ballard as he challenged for a ball into the Sunderland area. Merino was able to play on.
Eberechi Eze nearly cashed in of an mistake from Le Fée, who lost the ball on the border of the box, but the shot flew over the crossbar.
Isidor shot wide at the other end before a further long stoppage after a head collision between the midfielder and Jurriën Timber, who had to carry on with a bandaged head.
A tougher blow was to follow for bruised the visitors. The home team launched a free-kick into the visiting box and the captain resisted Rice to drive the shot past David Raya after it was knocked out. It was the first goal Arsenal had let in since their previous trip to the North East in September's end, when they had demonstrated their championship potential with a late win over the Magpies.
The Gunners had kept a club-record eight consecutive shutouts in every match since Woltemade's scored against them at St James' Park.
Sunderland made sure that it was a further uncomfortable visit to the area for Arsenal, who found themselves under pressure for periods after the interval.
They needed a moment of quality, and it came in the 54th minute. The midfielder won possession off his opponent and a flowing move featuring Eze and Merino culminated in the forward beating Robin Roefs at his near post.
The visitors pushed for a second goal and the coach introduced three changes to his offense â he brought on Brobbey, Talbi and Simon Adingra â in the middle of the second half.
Another moment of quality was not far away. Arsenal worked the ball from one flank to the other, and Trossard, on the edge of the area, found enough room to fire a right-foot shot into the top corner.
Raya had to be alert in the last 10 minutes as Sunderland pressed for a second goal, but was unable to prevent an acrobatic shot from Brobbey after the delivery was nodded into the penalty area. The goal was greeted by a deafening cheer.
Appropriately Ballard â similar to his teammate another ex-Gunner, this one developed in Arsenal's academy â had the final say with a flying challenge at the toes of Merino in the game's last action.