Arsenal's 2-0 defeat at Sunderland said so much about so many aspects of their play – their mental strength, their level of confidence, their raw quality.

The nature of the defeat, signalling the end of their last genuine chance of silverware this season, inevitably leads to grand conclusions based around small or simple incidents. ITV highlighted Sébastien Squillaci walking straight down the tunnel having being replaced, supposedly indicative of the lack of team spirit, while Roy Keane was outraged by so many players wearing gloves, an example of the lack of fight.

Tucked away was a smaller tactical point that can also be twisted into a microcosm of Arsenal's season. There are broadly two strategies a side can take when they do not have the ball. They can push up high and pressurise their opponents, or they can drop very deep, allow the opposition time on the ball in deep positions, but concentrate on remaining tight in their own third. This is the principal tactical debate in modern football – Barcelona have become the dominant side in Europe by pressing heavily, but the only side to deny Pep Guardiola three consecutive European Cups is Inter, who won the tournament by sitting deep in the 2009-10 season.

Of course, it is entirely possible to combine the approaches, which is basically what Martin O'Neill did this weekend. In the league meeting between the sides a week before, Sunderland sat very deep – they played fewer passes in the opposition half than any other side that weekend, and they allowed Mikel Arteta to play 100 passes, more than any Arsenal player had managed this season. It was an exaggerated form of standing off. But though they frustrated Arsène Wenger's side for long periods, Arsenal eventually found a way through. Aaron Ramsey steered in a shot from outside the box, while Thierry Henry found himself on the end of a cross to flick in the winner.

With that in mind, Sunderland used a hybrid approach. They often replicated that caution, but combined this with tenacity higher up the pitch when Arsenal were attempting to build attacks. A key part of Sunderland's gameplan was pressing the three Arsenal central midfielders when they received a forward pass, forcing Arteta, Ramsey and Alex Song to return the ball to where it came from. Arsenal's momentum was killed and they had to start again. When the away side did enjoy long periods on the ball and moved higher up the pitch, then Sunderland reverted to their deeper positions and packed the penalty box.

And this is the puzzle of Arsenal's current style – they are not good enough to overcome either problem. They conceded the first goal after midfield pressure, when Craig Gardner closed down Johan Djourou and forced a free-kick. They conceded the second when Sunderland sat deep, then broke quickly.

Arsenal have long struggled with deep and narrow defences. Stylistically, this should not be as much of a problem as in previous years – they no longer incessantly try to thread the ball through the middle, as they did with Cesc Fábregas the focal point with Samir Nasri and Andriy Arshavin coming inside from the flank. Instead, they play with width and pace, with Theo Walcott, Gervinho and Alex Oxlade-Chamberlain options out wide.

This naturally lends itself to playing against narrow sides, but Arsenal move the ball too slowly into wide zones, allowing the opposition to retreat into deep positions where going around the back four results in running out of space. Gervinho, for example, may frequently lose all sense of direction when in the penalty box, but he showed with one good bit of play in this game, when forcing a save from Simon Mignolet, that he can be effective when given the ball quickly and able to run in behind. Against Milan, Arsenal surely had to target the defensively poor Milan full-backs, but the ball never arrived at the wingers in potential one-on-one situations. Pitch-related concerns notwithstanding, it was simply a failure to maximise the area they were stronger in.

Now, they also struggle with pressure in midfield. Physical problems are a key factor; Arteta is too lightweight, as shown by how easily he was shoved off the ball by Stéphane Sessègnon for Sunderland's second goal. Ramsey is a fine competitor at his best, especially considering the severity of the injury he suffered at Stoke two years ago. But he has looked exhausted for weeks, and is currently the equivalent of a dying battery that has been shaken to squeeze more life out of it, when a fresh replacement is sorely needed. Song should be a fine physical force in front of the back four, but the insistence upon midfield rotation means he often ends up ahead of his two midfield colleagues, and is in no position to help.

In Wenger's glory days, Arsenal could deal with that physical attention. They were at their best with two imposing players in the centre – first Patrick Vieira and Emmanuel Petit, then later Vieira and Gilberto Silva. If the opposition tried to rough them up, Arsenal could overpower them. Even Mathieu Flamini was a decent solution. He was a smaller player, but fierce and combative. Much more talented players have left the club in the past few years, but Flamini's decision not to sign a new contract in the summer of 2008 was a significant blow.

The other option for getting around close attention in the centre is a sudden burst of pace and directness. The significance of Jack Wilshere's absence should not be overstated, but that is exactly what he brought to the side last season, and that is partly why he was appreciated by Arsenal fans, to an even greater extent than his fine performances would justify.

It is currently unclear what style of football Arsenal would want to play against. They are not good at dealing with sides pressuring them, and they are not good at dealing with sides who stand off and sit back. The only possible combination that works for them is a side foolish enough to play a high defensive line yet not close down sufficiently in midfield. It is no coincidence that Arsenal's only good performance against a top side this season, as Daniel Taylor notes, was away at Chelsea, who employed those tactics when they and André Villas-Boas were figuring each other out.

Maybe they still are – you half-expect that from a young manager trying to revolutionise a side's style of play. But the main benefit of Wenger's long-term reign has been consistency of approach, familiarity of ideals. For the first time since he joined the club, it is difficult to pinpoint precisely what Arsenal are good at.

Walcott fails to fire through the middle

The other interesting feature of Arsenal's game was Walcott's brief spell as a striker – he has frequently stated his desire to be fielded as a centre-forward, and here he finally got his chance. But the timing was wrong – late on Sunderland were sitting deeper and deeper, and though quick players are often used as super-subs because the opposition have tired, it often emerges that the player has no space to exploit. Walcott was desperate to run past the defence to use his pace, but his most significant contribution was being caught offside twice.

Three's company for Tottenham

Harry Redknapp switched to a 3-4-1-2 system for Tottenham's trip to Stevenage, with Gareth Bale used in a roaming role behind Louis Saha and Jermain Defoe. This was the first time Spurs had started a game under Redknapp with a back three, though he did switch to that system with relative success away at Stoke earlier in the season.

The obvious common theme between Stevenage and Stoke is their old-fashioned threat from set-pieces and high balls, and the primary reason for playing that system was probably simply to get extra height in at the back – it allowed Redknapp to play Younès Kaboul, Ryan Nelsen and Michael Dawson at the back. Maybe not the most radical decision you will see this season, but it shows that Redknapp thinks about the opposition before selecting his formation, and is not quite the tactical nihilist often portrayed.