Nacho Monreal is growing as a centre back
With Laurent Koscielny and Mathieu Debuchy still out injured, Arsene Wenger has been forced into using Nacho Monreal at centre back - an unfamiliar role for the left back.
After some growing pains to begin with, Monreal is showing more confidence in the role, and served well when bringing the ball out of defence against United. It is still unlikely to be his long term position at Arsenal, but there has been improvement from the Spaniard.
Aaron Ramsey has declined
Last season, Welsh midfielder Ramsey was the heartbeat of the Arsenal team, racking up ten goals and eight assists in the Premier League - and fans expected him to kick on from there this season.
However, Ramsey once again looked like a shadow of his former self, failing to really impose himself of the game. There were some decent passes to keep things ticking over, but Arsenal fans have come to expect more from Ramsey, who didn't pose much of an attacking threat.
Does Danny Welbeck deserve more criticism?
When Olivier Giroud suffered a serious injury in August, Wenger splashed out £16m in order to snap up Manchester United striker Danny Welbeck.
Whilst he impressed with a hat-trick against Galatasaray in the Champions League, Welbeck's Premier League record stands at just two goals in nine games, and he wasted more good chances against his former club on Saturday - which is cause for concern for the England international after Giroud's goalscoring return.
Fourth appears the best Arsenal can hope for
Arsenal have widely been known as the fourth place also-rans, with six fourth place finishes in the last nine seasons - and in the other three, they only came third.
Gaining Champions League football is great, but there has been absolutely no progress for almost ten years now, and yet another defeat for Arsenal leaves them 15 points behind leaders Chelsea after just 12 games of the season. At this point, fourth place seems like the best that Arsenal can hope for after a tough start to the season - and fans are unsurprisingly disgruntled.
Arsenal will miss Jack Wilshere
Whilst losing to a top four rival is a blow, Wilshere's second half injury just served to compound the misery on the Gunners faithful.
Wilshere's ankle injury looked a nasty one, and if the 22-year-old is out for a prolonged period of time, then that's a monumental blow to Wenger. Wilshere has often come in for criticism, but his recent form has shown that the Arsenal star can play a number of different roles in midfield, and the Gunners have to pray that he returns quickly.