Arsenal's January transfer window was certainly eventful: Two star attackers arrived, another three departed, and there's now an entirely different feel to the side up front. Their problem this season, however, has rarely been in the final third.
Instead, Arsenal have struggled defensively -- they're on a run of eight league matches without a clean sheet, and have a terrible goals-against record of 35 in just 26 games -- a worse record than the five sides above them, plus Burnley. Brighton and Leicester have conceded the same number of goals; Newcastle only one more; Swansea, Bournemouth and bottom-placed West Brom only two more.
Perhaps some of those are unfair comparisons -- the likes of Burnley and Brighton have good defensive records because they're simply very defensive overall, and have scored fewer than half of Arsenal's 51 goals. But the point remains: Arsenal aren't struggling to keep pace with the other Champions League challengers because of their attack, where they've scored the same number of goals as Manchester United and Tottenham, and more than Chelsea. It's their defensive record holding them back.
Some would suggest this is a familiar problem for Arsenal, which isn't entirely true. In three of the past five seasons, they have conceded fewer than a goal a game, and in 2015-16 they conceded only one more than the two best defensive sides in the league, Tottenham and Manchester United. This is a relatively new issue, and if Arsenal keep up their rate of concessions, they'll end up shipping more than 50 league goals for the first time since 1983-84 -- for context, the season Tony Adams made his Arsenal debut.
This weekend's North London derby could prove a particularly stark contrast. Tottenham remain one of the Premier League's best sides without possession, pressing aggressively and keeping a high offside line that the old Arsenal back four would admire. Toby Alderweireld came through the midweek FA Cup win over Newport and could reprise his partnership with Jan Vertonghen, arguably the best in the Premier League. Spurs had the best defensive record in last season's Premier League, the joint-best the season before.
So what, precisely, are Arsenal's problems? It can probably be broken down into five main factors.
First, the midfield hasn't been impressive protecting the defence. Across the Premier League, teams are increasingly keeping two holding midfielders in position, to prevent opponents from finding space between the lines, and to guard against the centre-backs being dragged out of position.
Arsenal have done this only sporadically. Their best midfielder this season has been Aaron Ramsey, whose game depends upon constant forward runs into goalscoring positions. It has often paid off -- last week's hat trick against Everton was the perfect example. But at other times, like in Arsenal's 4-0 thrashing at Liverpool in August, Ramsey rather neglects his defensive duties, remaining too high up the pitch. He needs to learn when to sit, and when to go.
When he goes, he isolates Granit Xhaka. The Swiss midfielder has found life in the Premier League difficult so far -- he lacks the mobility of N'Golo Kante, the new template for defensive midfielders, and is often forced into clumsy or cynical fouls to halt opposition breaks. He looks more comfortable when partnered with Mohamed Elneny, who has shown intelligence to drop between the centre-backs at times, too. But Arsenal haven't been secure in that zone, and arguably haven't ever replaced Mikel Arteta, who wasn't a natural defensive midfielder but boasted tremendous positional awareness.
Second, changing the system so frequently has caused uncertainty and a lack of good relationships between defenders. Arsenal started the campaign with the 3-4-3 that Arsene Wenger switched to last spring, but in December began to use a 4-3-3 system on and off, regularly alternating between a four-man defence and a back three. For last weekend's 5-1 win over Everton, meanwhile, they used a 4-2-3-1, which necessitates a different midfield block without possession.
Some sides are capable of switching between systems and still remaining secure -- Tottenham are a fine example. But regular formation changes have never been a key part of Wenger's approach, and it seems obvious that defensive cohesion has suffered.
Third, the personnel have changed too often for Wenger's liking. This season has seen Laurent Koscielny, Nacho Monreal, Shkodran Mustafi, Rob Holding, Per Mertesacker, Calum Chambers, Sead Kolasinac and even Francis Coquelin all have stints at centre-back, either in a four or a three-man defence. Arsenal lack a defined partnership, like Koscielny and Mertesacker a couple of seasons ago.
Fourth, and perhaps most worryingly, Arsenal's first-choice centre-backs haven't looked solid this season. Koscielny, for so long one of the Premier League's most consistent defenders, excellent at nipping in ahead of opponents and winning one-against-one duels, is 32 and looks less mobile, partly because of persistent Achilles' tendon problems. The Frenchman might be able to change his game and become a more old-school defender. For now, though, he's not producing the form of yesteryear.
His centre-back partner Mustafi, meanwhile, has made too many mistakes. The German has something of the Thomas Vermaelen in his playing style, always determined to come forward, be positive and win the ball quickly -- but is outwitted too often, and caught ahead of the ball. This was particularly inexcusable when playing between Chambers and Holding, two young defenders who would have expected more consistency and leadership from a World Cup winner.
Fifth, and finally, Arsenal seem to wilt late on. They've conceded 12 first half goals -- and 23 after the break, which could prove particularly disastrous if Spurs repeat their performance from Anfield, where they improved hugely in the second period.
This weekend, all eyes will be on Harry Kane, with the Spurs striker having scored six in six against the Gunners. He remains the most likely individual matchwinner, but it's Tottenham's organisation without possession, and their solid defence, which Arsenal should admire more