Ole Gunnar Solskjaer’s 100th match in charge of Manchester United ended in a 1-0 defeat to Arsenal after Pierre-Emerick Aubameyang scored from the penalty spot.
The Gunners were much the better side in the clash at Old Trafford on Sunday and Aubameyang's 69th-minute spot-kick secured their first victory at Old Trafford in the Premier League since September 2006.
United created few opportunities in front of goal and the contest was settled after Paul Pogba was deemed to have fouled Hector Bellerin inside the area.
The result helped Arsenal move up to eighth place in the table on 12 points, ahead of United in 15th, with the Red Devils winless at home in the Premier League after four games this season.
This was the first time since 1936 that the sides had met each other with both of them languishing in the bottom half of the table, and it was Arsenal who climbed out.
Even though the Premier League season is only seven games old, scrutiny will increase on Solskjaer, with the tactically-astute performance of Mikel Arteta's side much more encouraging.
Arsenal started brightly and Aubameyang was within a whisker of getting a touch on Bellerin's low cross as he looked to put the Gunners ahead.
United registered the first attempt on target when Marcus Rashford whipped a teasing ball from the right across the penalty area for Mason Greenwood, who saw his low angled shot saved by Arsenal goalkeeper Bernd Leno at the near post.
But it was Arteta's side who finished the first half the stronger, as Wililam's curling effort grazed the crossbar while Bukayo Saka headed just wide from a good position.
Indeed, United's solitary effort meant they had their fewest shots in the first half of a Premier League home game since having none against Manchester City in October 2015.
Arsenal caught United in possession six minutes into the second half and Aubameyang curled a shot past the post, while Harry Maguire headed wide for the hosts not long afterwards.
Thomas Partey's long-range effort was comfortably saved by David De Gea before the moment came when Pogba clipped Bellerin's ankle and Aubameyang calmly found the right corner.
Solskjaer threw on veteran Uruguay striker Edinson Cavani with 15 minutes left, but apart from a few speculative long-range efforts, it was a tame finish from United as Arsenal comfortably handled long balls pumped into the box.
What does it mean? Solskjaer in the spotlight
Solskjaer has won 55, drawn 21 and lost 24 of his first 100 games, which is a record better than his long-term mentor Alex Ferguson (48 wins, 31 draws and 21 losses), but tellingly behind the man he replaced Jose Mourinho (62 wins, 23 and 15 defeats).
After this result made it three defeats and one draw from their first four home Premier League games, it would have been interesting to see what the reaction of the Old Trafford crowd at full-time would have been had the stands been packed.
Arsenal's performance was full of promise for Arteta, who became just the second manager in their history to win both of his first two games against United, after Herbert Chapman in 1925-26.
Aubameyang keeps his cool
Aubameyang had gone five Premier League games without a goal but he kept his cool to send De Gea the wrong way with a clinical penalty kick.
He became the first Arsenal player to score a penalty at Old Trafford in the Premier League, with neither of the previous two attempts being converted by Robin van Persie in 2011 and Gilberto Silva in 2006.
Pogba embodies careless United
France international Pogba once again failed to show the composure required in such a big game.
He has now given away three Premier League penalties since Solskjaer took charge of United, with no other player doing so more than once for the Red Devils during his tenure. Indeed United have conceded five penalties in their last seven Premier League home games, having given away five in their previous 101 such games.
What's next?
Both clubs are in European action in the coming week. United head to Turkey for a Champions League Group H clash against Istanbul Basaksehir on Wednesday while Arsenal host Norwegian side Molde on Thursday in Europa League Group B.
