A bizarre last-gasp winner from Divock Origi at Anfield was a fitting way to end an excellent triple-header of Premier League action on Sunday. Liverpool proved their mental resilience in the derby a day after Manchester City had to work just as hard to overcome Bournemouth, keeping the gap at the top to just two points as we approach the hectic Christmas schedule.
Here are three things we learnt from the weekend action:
1) Both Arsenal and Spurs are shown the perils of using a back three
In a wild game at the Emirates Unai Emery and Mauricio Pochettino repeatedly swapped formations in the most interesting tactical battle of the Premier League so far, and amid the often confusing system changes we learnt exactly what can go wrong with an improvised back three. Spurs dominated the final 20 minutes of the first half and Arsenal the final 20 of the second as the two teams chopped and changed their line-ups.
Arsenal's back three was put under pressure by the fluidity of Dele Alli, Harry Kane, and Heung-Min Son, who created three-on-three opportunities thanks to the high starting position of the Gunners wing-backs and Christian Eriksen's gradual control of the midfield battle. As a back three tries to spread across the width of the pitch, inevitably gaps appear between the centre-backs and on the outside; front threes tend to come out on top.
Emery eventually changed formation, first to a 3-4-1-2 and then, when Pochettino reacted to this by dropping Eric Dier back to form a back three himself, to a diamond 4-4-2. This final change put Aaron Ramsey behind Pierre-Emerick Aubameyang and Alexandre Lacazette, with the Welshman making late forwards runs to form a front three.
Dier was at fault for the final two Arsenal goals, again displaying the perils of three forwards against three centre-backs. There was a strange symmetry to how the two sides reversed roles here – and in both cases of three-on-three the attacking side came out on top.
2) Everton's 4-4-2 creates an open game that highlights Marco Silva's influence
Everton's surprise 4-4-2 formation was very nearly the perfect way to nullify Liverpool and win in attacking style, and despite Divock Origi's late winner Marco Silva will be proud of his side's performance. Gylfi Sigurdsson and Richarlison performed well together, cutting off the passing lines to the Liverpool midfield to limit the hosts' creativity.
More importantly, Everton boldly committed men forward and looked to bring their overlapping full-backs into the game as frequently as possible – the clearest sign yet that the Toffees are beginning to take on the hallmarks of their new coach. Lucas Digne and Seamus Coleman had more touches of the ball than any other Everton players, with 65 and 70 respectively, to remind us of his Hull City team and Andrew Robertson's rise to fame.
Not many clubs would be happy to create an open end-to-end game at Anfield, but by playing lots of long balls forward (and fielding only two midfielders) Everton backed themselves creatively; the direct forward passes from both sides stretched the pitch vertically, leaving huge spaces for counters and counter-counters. Andre Gomes was outstanding once again, while Idrissa Gueye controlled Liverpool for the vast majority of the game.
3) Pedro's runs help Chelsea as Jorginho breaks free
Perhaps the most important lesson from Chelsea's 2-0 win against Fulham was that marking Jorginho out of the game is more difficult than Gylfi Sigurdsson and Dele Alli made it look. Maurizio Sarri has stubbornly refused to swap his midfield around despite pressure from the media, and he was vindicated on Sunday as Jorginho easily broke free of Tom Cairney to dominate the game. His short interchanges with Matteo Kovacic set the tempo for a simple home win.
Claudio Ranieri's team struggled to stay compact in the first half, further evidence that it will take some time for the new boss to sure up their soft centre. Jean-Michael Seri's error for the fourth-minute opener typified the too-open Jokanovic-era Fulham; the full-backs and other midfielders were already in the Chelsea half, leaving Seri helpless when receiving the ball.
Chelsea still look predictable in attack, although Pedro's contribution was noteworthy. The Spaniard frequently made runs on the shoulder of the last defender, giving Jorginho and N'Golo Kante a more direct forward route and pulling the Fulham defence backwards – and therefore out of shape. They'll need greater variety against the bigger clubs, but for now Jorginho can still flourish from the base of midfield. He completed 87 passes, up from 50 and 51 in his previous two league games.
Best of the Week – West Ham's attacking performance
They were a little too open in midfield, allowing Newcastle United far too many opportunities to score, but Manuel Pellegrini deserves praise for West Ham United's attacking 4-4-2 formation. Javier Hernandez, who has always worked better with a striker partner, used Marko Arnautovic's eye-catching playing style to make unseen runs in behind, grabbing a brace for the first time this season.
Felipe Anderson's good form continued with his fourth goal in four games and Robert Snodgrass was surprisingly effective from the right wing. This was the sort of attacking, though vulnerable, West Ham performance we expected from Pellegrini when he arrived in east London; they can't afford to be so open very often, but against relegation candidates the 4-4-2 could be the way to go.
Worst of the Week - Man Utd's negativity
Jose Mourinho selected seven defensive players for the trip to one of the Premier League's worst clubs. He played a back three despite the fact Southampton had scored just 10 goals in 13 games. He played both Ander Herrera and Maroune Fellaini deep in midfield, leaving Paul Pogba with only two attackers to aim for. In terms of approaching matches with the right mentality, it was a new low for Mourinho at United.
It took two brilliant pieces of play from Marcus Rashford to salvage anything from this match, and yet with the scores level at half-time Mourinho could easily have swung the game in his favour. Instead, he waited until the 77th minute to make his first attacking change… and in the end brought on two forwards to replace the two already on the pitch. It's no wonder United are already 16 points adrift of the league leaders Manchester City.