For more than 50 minutes, Arsenal dominated Manchester United, creating chances at will against the most makeshift of defenses. Then it all, dramatically, suddenly and all too predictably, went horribly wrong. Another ankle injury to Jack Wilshere was quickly followed by Antonio Valencia’s strike across goal being turned in by Kieran Gibbs, moments after the Arsenal defender had collided haplessly with his goalkeeper to take Wojciech Szczesny out of the proceedings, too.

A match Arsenal should have won comfortably against a team riddled with injuries and early on still visibly uneasy in a reintroduced 3-5-2 formation, ended with a 2-1 loss and a first away win for Manchester United manager Louis van Gaal. Olivier Giroud’s made a spectacular return from injury with a stoppage-time thunderbolt, but it was too little too late after Wayne Rooney had earlier added a second for the visitors on the break.

Arsenal have now failed to win in three matches. On Wednesday against Borussia Dortmund, their hopes of topping their Champions League group could well come to the end. Their ambitions to end a more than decade-long wait for a Premier League title have surely already gone by the wayside. After 12 matches, Arsenal have just four wins, 17 points and sit seventh in the table, a massive 15 points behind leaders Chelsea. It is now their worst start to a league season in 32 years. And they are now two points behind Manchester United, whose second win on the bounce sees them rise up to fourth and with their quest for a return to the Champions League on track despite a most testing start to Van Gaal’s reign.

Such a position looked a long way off in the early stages of Saturday evening’s contest in north London. Van Gaal started with a back five of Valencia, Paddy McNair, Tyler Blackett, Chris Smalling and Luke Shaw after the club’s latest rash of injuries. It soon got worse, still, when Shaw was forced off to be replaced by Ashley Young. Arsenal looked set to prosper. In the first 15 minutes, three clear chances were created as Arsene Wenger’s team besieged a nervy and uncertain backline.

Danny Welbeck should have punished his former club, but instead perhaps showed why Van Gaal was willing to part with him on the final day of the transfer window. First he showed a lack of conviction when having an effort blocked by McNair and then the England forward headed over after having gotten free to meet a cross from the continually-dangerous Alex Oxlade-Chamberlain. The best opportunity, though, fell to Wilshere. Played clean through by Welbeck after more relentless Alexis Sanchez pressing, the midfielder’s effort was tame and David de Gea guessed right to make a save.

It was just the first of a series of impressive contributions from a goalkeeper who began his United career as a liability but is now so regularly a savior. His presence was needed, as it wasn’t until the half-hour mark had passed that the visitors enjoyed any meaningful possession and managed to mount an attack of note. Angel di Maria, allowed freedom alongside Robin van Persie and in front of Rooney, almost helped United garner a shock half-time lead.

Arsenal regained the momentum, but again failed to capitalize at the start of the second half when De Gea stood up well to deny Welbeck. For all Arsenal were in control, there was the inescapable feeling that not only would they not win, but that they could well lose. Lacking the killer instinct in the final third, they retain a soft center that means the opposition always has a chance if they can simply hang around long enough.

That’s exactly what happened. Just a minute after Wilshere was forced to admit defeat to another in a long line of ankle problems, Arsenal conceded the type of goal that has become all-too familiar for far too long. Gibbs and Szczesny collided in going to meet Young’s cross, leaving them both grounded before Gibbs stuck out his leg to unwittingly deflect Valencia’s blast into his own net.

There were half-chances for Arsenal to get back level, but never the belief that they could rebound from the blow of going a goal down and losing both Wilshere and Szczesny to injury. To their credit, Manchester United were now defending with more resilience. Several committed blocks came in and Smalling was playing the role of the team’s most experienced defender impressively. Van Gaal was again making the most of his limited options and finding a way to get the job done in trying circumstances. The same could not be said for his counterpart on the Arsenal bench.

As well as frustrating Arsenal, Van Gaal showed real boldness and shrewdness to keep two strikers on the pitch, replacing Van Persie with James Wilson, allowing his side to take advantage of Arsenal’s predictable over commitment going forward. With five minutes of normal time remaining, that plan paid dividends. United broke two against one, Di Maria played in Rooney and he coolly dinked over Arsenal’s substitute third-choice goalkeeper Emiliano Martinez.

The win should have been made more emphatic when Rooney returned the favor for Di Maria, but Manchester United’s record signing couldn’t repeat his teammate’s finish. Giroud’s unstoppable blast into the top corner in the middle of eight minutes of injury time briefly raised hopes and some cheers inside the Emirates Stadium, but the boos that rang out at the final whistle soon told the true story.