The busy Christmas fixtures are finally over, and after yet another period of injuries, sloppy football, and low-scoring games the cries for a major overhaul of the Premier League fixture list are only growing louder.

It can be difficult to keep track of everything that's happened. Stoke City's slide shows no signs of stopping and West Bromwich Albion are now in deep trouble, while Liverpool have shown a new resilient side and Manchester United have stumble upon a new formation.

Here are three things we learnt from the action:

1) Mourinho's improvised tactics point to a more fluid direction for Pogba and United

Two quick counter-attacking goals, defined by individual skill in possession and world-class movement by the supporting cast, handed Manchester United a 2-0 victory at Goodison Park on New Year's Day. It was a second-half of football that contained all the ingenuity and tactical fluidity Jose Mourinho's side have been lacking this season – and it was thanks primarily to their use of a striker-less 4-3-3.

Injuries to Romelu Lukaku and Zlatan Ibrahimovic handed Anthony Martial a chance to play up-front, and the Frenchman dropped deeper to become a false-nine. This is exactly what modern strikers should do, but it is a blind spot for Mourinho, who still insists upon less mobile but more powerful centre-forwards. Martial's quick link-up play with Jesse Lingard, Paul Pogba, and Juan Mata was more impressive than anything United have managed this season with Lukaku up front.

Pogba benefited greatly from the tactical shift because, in a 4-3-3, he gets plenty of support from two midfielders. Ander Herrera's covering role meant the Frenchman poured forward more aggressively, finishing the match with two assists. It is hard to imagine Mourinho will continue with this system once Lukaku returns, but he should.

2) Arsenal & Chelsea's end-to-end game shows why 3-5-2 can be the most entertainingly flawed formation

The 2-2 draw between Chelsea and Arsenal at the Emirates on Wednesday evening was one of the most entertaining matches of the Premier League season, primarily because both sides used a version of 3-4-3 that separated the defensive line from the front line by far too large a gap.

Presumably because they were rattled by the attacking aggression of their opponents, both teams' wing-backs consistently dropped deep to make a flat back five while Eden Hazard and Alexis Sanchez floated alongside strikers Alvaro Morata and Alexandre Lacazette. The result was two teams playing a flat-ish 5-2-1-2 in which the five defenders backpedalled and the opposition front three pushed up to join the line.

This created a very long pitch – and thus unbelievably large open spaces between the two defensive lines, in which just four midfielders (two from each side) occupied the space. It is no wonder Tiemoue Bakayoko looked so lost and Mesut Ozil had such a good game.

3) Leggy Man City performance suggests strength-in-depth not what it seems

Manchester City's 0-0 draw with Crystal Palace on New Year's Eve was put down to the visitors' tiredness during the run of festive fixtures, but a confident 3-1 victory over Watford just two days later makes that theory redundant. The real reason was that four unfamiliar players were on the pitch at Selhurst Park, and not one of them moved confidently enough to disrupt Palace's defensive shape.

Danilo and Eliaquim Mangala looked shaky in possession (Palace could have won the game had Roy Hodgson played Wilfried Zaha on the right, to confront these two, rather than on the left), and more importantly Ilkay Gundogan and Bernardo Silva seemed fragile. Neither player created space with their movement or conjured slick passing triangles when on the ball, reflecting their lack of experience in the Premier League.

City were nothing like their usual selves as a result, suggesting there isn't much strength in depth at the club. The league title is already over, but if Kevin de Bruyne and David Silva become tired in the Spring then an invincible season probably won't happen.

Best of the Week – Liverpool's resilience

Jurgen Klopp's Liverpool are gradually improving on all aspects of their play this season, and the German will be delighted with the character his side showed over the Christmas period. So often on the end of disappointing draws, Liverpool showed great resilience to come back from a goal down to beat Leicester City and then score a late winner against Burnley two days later.

Adam Lallana's return from injury no doubt had a big impact. The England midfielder was instrumental at Turf Moor, making four key passes and controlling the tempo of the match in Philippe Coutiho's absence. Liverpool might not miss the Brazilian after all.

Worst of the Week – West Brom's tactical simplicity

Alan Pardew appears to have been found out. West Bromwich Albion are now on a run of 20 Premier League matches without a win as Pardew flounders desperately in his new job. The most disappointing performance so far was the 2-1 defeat at West Ham United, in which the simplicity and predictability of the Baggies' tactics made for painful viewing.

Pardew likes to play direct counter-attacking football via quick wingers, and he has tried the same thing at West Brom despite the club not having the right playing staff to implement his tried-and-tested philosophy. David Moyes, a much more considered and reactive tactician, easily stumped his opponents' attempts to counter through Jay Rodriguez.