1 Arsenal remain sick of the sight of Wayne Rooney
The Manchester United striker's pre-match barbs were perceived as a sign that for the first time in ages his club saw Arsenal as a relevant danger. He certainly played as if he had something of a personal point he was keen to make – and where better to make it than on the pitch. Rooney made his presence felt all over the big-match stage to pile pressure on United's opponents. His indefatigable work rate, and leadership by example, put United in the driving seat and kept them there. In the end, he wasn't wrong – come the final whistle Arsenal were sick of the sight, once again, of a player who has contributed in a big way to the end of an unbeaten sequence for the third time (twice with United and once with David Moyes' Everton). After a summer of awkwardness, when his relationship with the club was the subject of genuine concern, his name was being chanted with relish by the Old Trafford crowd. Their chief chaser of causes was excellent.
2 Zonal marking under the cosh once again
Arsenal actually had more corners than United – and more possession for that matter – but it was one of United's that saw their two richest talents combine decisively. Arsenal were coping well enough until they hiccupped over a poorly defended set-piece. Rooney's corner was enticingly delivered, and the running leap, as opposed to the more static start of the visiting defenders in zonal marking mode, gave Robin van Persie the advantage to steer his header with unerring precision. United had practised set-pieces as a potential weapon to capitalise on the number of small players in the Arsenal line-up. They must have been pleased to see Per Mertesacker, the organiser, and the glue in Arsenal's defence, out with a bug. It was a substantial loss. There was less cohesion in the back four as a whole without the influence of the giant German.
3 Back with a bang on the big occasion
United, having lost against Manchester City and Liverpool, and drawn a home match with Chelsea earlier in the campaign, knew that any slip against Arsenal would lead to serious questions about their capabilities against title rivals. It was important for them to reassert themselves in terms of serving up a little dose of Old Trafford fear factor as well as the obvious need for a points booster. For a team that was stuttering at home in the autumn, with defeat to West Brom and a draw against Southampton, it feels like something resembling normal service has resumed. The added bonus of dropped points for Arsenal, City, Chelsea and Tottenham has made for a perfect weekend.
4 The new kids on United's defensive block so solid
Phil Jones and Chris Smalling played key roles in repelling Arsenal's attempted second-half comeback. Jones deserves an extra pat on the back because his midfield role in the first half, before withdrawing into the back four to replace Nemanja Vidic, helped to give United the platform to win. Moyes had been conscious of the possibility of being outmanned in midfield, but by pairing Jones, an uber-enthusiastic blocking machine, with the more controlled Michael Carrick in the first half, Arsenal's passing game was restricted. Jones hurled himself at anything that moved in yellow to great effect, stopping half-chances at source. The England man barely seemed to feel the crunching clash of heads with Wojciech Szczesny. He still has his uses for Moyes in both departments, but you cannot help feeling that he will profit from a fixed position eventually.
5 Arsenal need a striker with pace
Olivier Giroud's frustrationwas written all over his face. His pained expressions throughout the game reflected how nothing would stick, chances didn't fall right, 50-50 attempts to win the ball were called against him time and again. He has been crucial to his team's early surge to the top of the Premier League table but the lack of an alternative, or a variant, means that an off-day led to a blunt Arsenal. There were enough glimmers in the second half for Arsène Wenger's team to have snatched something from the game, but when it is not clicking up front, it is useful to be able to look at the bench and think there is a goal or two in reserve. Nicklas Bendtner cannot be relied upon. The long-term injuries to Theo Walcott and Lukas Podolski told here. Serge Gnabry, the teenage substitute, showed just how important it is to have an outlet with speed on his side.