UK Edition
Whether through choice, at the request of his players or in admiration of Chelsea's success playing with a back three, Arsenal manager Arsene Wenger decided a match against Middlesbrough was time to try something new. He hasn't looked back since.
"I think what I did is just to give a bit more security to a team who conceded three goals in the last three away games," said Wenger after the FA Cup semi-final win over Man City last season. On top of adding that security, Arsenal started winning games again - nine out of their final 10 ended in victory last season, including the FA Cup final.
They've already won the Community Shield. Could it... is... is this... is this Arsenal's year? Does a back three really solve their problems?
How the new system works
To help prevent his side conceding all of the goals, Wenger replaced one attacking player with a defensive one. The 4-2-3-1 became a 3-4-2-1. Lovely.
By the time the FA Cup final came around, the back three featured Nacho Monreal at left centre-back (LCB), Laurent Koscielny in the middle (CB) and Rob Holding at right centre-back (RCB) - the results yielded from this shape suggest it really works.
The wing-backs have more freedom to get forward because of the safety net of an extra defender, which means the forwards, Mesut Ozil and Alexis Sanchez, can move inside the pitch to play in positions behind and around the striker.
And by swapping the number 10 slot for a centre-back, Wenger frees up space for both Ozil and Sanchez to operate as 10s when they want to.
In Antonio Conte's 3-4-3, the two midfielders stay deep, providing cover to the three. In Wenger's, Granit Xhaka and a partner tend to have different instructions depending on the opposition.
Why this can be a problem
By replacing an attacking player with an extra defender, when Arsenal have control of the ball higher up the pitch, they are a creative player short.
As a direct example, Arsenal played Sunderland in the third last game of the Premier League season. David Moyes' side were awful and defended deep in order to frustrate Arsenal's far sexier players, but Wenger went with the same stable 3-4-3 that had begun churning out results.
What followed was 70 minutes of nonsense, as Arsenal troubled one of the worst Premier League teams in memory but lacked that missing edge to make the break through.
They couldn't create the clear chances needed against a team begging to be thrashed. And so in the 72nd minute, on came Alex Iwobi and Danny Welbeck, the team reverted to a back four and duly put two goals past Jordan Pickford.
Statistically the change to a 3-4-3 has made little difference. Arsenal still keep ~59 per cent of possession, have around 14.9 shots per game and cover 108.3km per game instead of 110.6km. In fact, the only noticeable change is in how often they clear the ball, intercept and tackle. In a back four, they cleared the ball 21.6 times per game but do so more in a three, making 23.75 times per game.
They now only make 9.75 interceptions per game instead of 15.23 and make fewer tackles too, now recording 16 per game instead of 18.
It's difficult to read too much into these because of the different teams Arsenal played in those eight Premier League games compared to the previous 30, but it suggests that despite still enjoying the share of possession, they are quicker to get rid of the ball in compromising situations. Is this because centre-backs are less likely to spot a forward pass when under pressure, or is it simply better game management? Is it better to always keep the ball flowing or to sometimes just punt the thing away and reorganise?
Why they miss Santi Cazorla so much
A lot of teams like Man City, Liverpool and even the old Arsenal, form a back three of sorts when they attack, with a central midfield player dropping deeper to act as a playmaker between the two centre-backs. When Yaya Toure, for example, stays deep he isn't a defender, but rather a creative midfielder providing cover, able to recycle play and facilitate extended passages of play in the opposition half. Per Mertesacker isn't going to unlock a defence with a through-ball from the half way line, but someone like Jordan Henderson, who does it for Liverpool, definitely can.
In Santi Cazorla, Arsenal have a player who can act as that pivot. With him in the team, there was no need for extra defensive cover either because he operates as a Andrea Pirlo/Yaya Toure type whereas someone like Francis Coquelin is drawn towards the ball like a moth towards light. Some players just know when the right time to go forward is - Cazorla is one of them.
However, there are signs that Granit Xhaka might actually be the perfect replacement. His Arsenal career didn't start amazingly well and his tendency to pick up bookings and red cards were the exclamation points on some mixed performances, but at some point in the second half of last season, something clicked.
There has been a notable difference in Xhaka's influence on the pitch since the new year - nearly all of Xhaka's key statistics improved after January. He created 25 chances instead of 10, made two assists instead of 0 and his passing accuracy improved ever so slightly.
The Swiss now makes fewer interceptions and tackles too, focusing on keeping the ball and distributing it instead of trying to win it back - and this is exactly why Wenger bought him. The most important thing to note is in the first half of the season Xhaka made 61 passes per game, in the second this went up to 81.2 - he is far more involved in play now.
Perhaps he's taken time to adjust to the league, style of play and his teammates - whatever has happened, Xhaka is now the player that Wenger signed for so much money last summer.
For too many seasons, Arsenal have conceded silly goals on counter-attacks and been caught short when in possession. Wenger has attempted to fix this with a back three and it coincided with an excellent run of form - when Arsenal inevitably falter this season, will he persevere with that same shape?
With Xhaka stepping up to the level he's capable of - he was superb in the Community Shield win over Chelsea - and a sensible midfield partner next to him, Arsenal can quite easily revert to one of Wenger's preferred tactical shapes and history suggests this is what will happen. They started last season playing in a 4-4-1-1, changed it slowly during the season and then snapped to a 3-4-3 when the team looked shaky - Wenger has started adapting his side to their opponents, which marks a real change in his approach to matches.
If Arsenal start well and they grow in confidence, they won't need to be quite as cautious - especially against teams who can't play the sort of beautiful football that Wenger's team is capable of - and we might see Wenger change the tactical set up for different games.
Something had to change last season, Wenger made that switch and it worked. Arsenal need to get it right from kick-off this time and not be afraid to tinker with a winning system.