Mikel Arteta's impact at Arsenal has been immediate and impressive. Having performed with a clear plan and real intent for perhaps their best 50 minutes of the season against Chelsea last week, they raised their game again to beat Manchester United with rare distinction on New Year's Day.
Why haven't they performed like this more often? David Luiz's and Arteta's post-match admissions that Arsenal simply weren't - and still aren't - fit enough to play with intensity for 90 minutes was an instant, telling and damning explanation. So too Luiz's reference to a lack of belief among the Arsenal players. Did they simply not believe in what Unai Emery was preaching? Seemingly not.
Arteta's other instant trick has been the most straightforward of all: play players in their proper positions. Is anyone surprised that Lucas Torreira is better as a midfield snarler than a No 10? Or that Mesut Ozil is more comfortable in a central role in a defined 4-2-3-1 system? And that having a settled formation offers a stable base on which good performances can be delivered?
Arteta has not yet made Arsenal fit. That will take time and training. But he has at least already made them fit for purpose.
The new manager bump is well and truly over at Tottenham. Over the four festive games, Jose Mourinho's side have picked up just four points and were once again frustrated by a team who are still considered at risk for relegation.
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It seemed like Tottenham left their tactics book at Carrow Road too because unlike their draw against Norwich, Spurs looked out of ideas on how to beat a confident Southampton side and their passing game left little to be desired. Harry Kane had little service, Dele Alli was kept mighty quiet and they were over-run in midfield, with Saints captain Pierre-Emile Hojbjerg, in particular, an absolute force.
Tottenham also suffered two huge injuries to add to their on-field frustrations, with Tanguy Ndombele taken off in the first half before Kane pulled his hamstring when scoring an offside goal - something that typified their horrendous afternoon on the south coast. It was all too much for Mourinho as he went over to voice his displeasure at apparent Southampton time-wasting. He confronted Saints goalkeeping coach Andrew Sparks before receiving a yellow card from referee Mike Dean, which he fully accepted even while branding Sparks an 'idiot' after the game.
The last two games have laid bare all of the issues that Mourinho still has to deal with. Some may say that three games in a week played its part, and that is true to an extent, but on Wednesday, Tottenham were still stuck in 2019 and that will be a real worry. There is plenty more work needed across the board and with Liverpool to come in ten days time, live on Sky Sports, that must begin immediately.
For all their problems in defence this season, Manchester City's switch to a five-man back-line, or three-man central defence, could work wonders as they look to salvage their season.
Eric Garcia was again far more composed than Nicolas Otamendi, with Rodri dropping into the back-line to make it a three alongside Fernandinho, giving City far more stability. The 2-1 scoreline was not representative of the champions' dominance.
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Are they preparing for next month's Champions League last 16 against Real Madrid? Interestingly, Pep used a five-man defence in a pre-season friendly against Real in the summer of 2017. The result? 4-1 to City.
At the other end, it was the job of Gabriel Jesus, helped by Riyad Mahrez, to give City their bite as they rested Raheem Sterling and Sergio Aguero. It is quite something that Jesus (69 goal involvements in 75 starts) and Mahrez (35 goal involvements in 46 starts) are not in everyone's preferred City XI. Their strength in depth in an attacking sense is still something to behold.
David Moyes could not have possibly dreamt, as he lay in bed while the New Year fireworks crackled outside, of a more perfect return to the West Ham dugout than their 4-0 win over Bournemouth.
His previously-porous defence restricted the visitors to a single shot before the break, by which time his own side were already 3-0 up and cruising. Mark Noble led the charge but an encouraging performance - and superb goal - from Sebastien Haller, only his second in his last 12 games, would have pleased Moyes too.
As the game progressed things got even better as Felipe Anderson, horribly out of form and without a goal to his name this season, strode through to get himself off the mark.
It is going to be a long ride for Moyes, with plenty of bumps in the road along the way, but in terms of one of his initial battles - winning over any doubters that he is the man for the London Stadium job - this is a big step forward.
Ladies and gentlemen, Southampton have finally arrived in the Premier League for the 2019/20 season. Before the game against Spurs, Ralph Hasenhuttl said the 9-0 drubbing by Leicester in October was the turning point in their season, and this superb 1-0 victory was proof of that.
From the outset, Southampton were by far the better side. They had more energy, better play and looked hungrier for the victory. There was also the wonderful winner from Danny Ings as he left Toby Alderweireld on his knees before sweeping home past a baffled Paulo Gazzaniga. Ings is enjoying his best scoring spell in the Premier League Premier League and Saints' rapid climb up the table is inextricably linked, which is nice to see after some serious injuries kept Ings sidelined for much of his spell with Liverpool.
Hasenhuttl said after the game that the win was Southampton's best home performance under him so far and it is hard to disagree. The Saints have claimed 10 out of 12 points over the festive period which has catapulted them into mid-table, something that looked a far-reaching fantasy after that horrible evening against Leicester. Hasenhuttl has finally found the winning formula.
So often this season Jack Grealish has been the main man for Aston Villa, and if he can keep producing to this level Dean Smith's side will have every chance of beating the drop come May.
Time and time again Villa's captain has stood up to be an influential figure for his side this season, and at Burnley it was no different.
The 24-year-old was the outstanding player on the pitch and his powerful strike into the top corner for Villa's second was the icing on the cake to what was a brilliant performance.
Grealish now has the most goal involvements by an English midfielder in the Premier League this season ahead of Dele Alli, James Maddison, Todd Cantwell and Mason Mount.
🏴 Most goal involvements by English midfielders in @premierleague this season:— Sky Sports Statto (@SkySportsStatto) January 1, 2020
1⃣1⃣ GREALISH (6 goals, 5 assists)
9⃣ Dele Alli (6 goals, 3 assists)
8⃣ Maddison (5 goals, 3 assists)
7⃣ Cantwell (5 goals, 2 assists)
7⃣ Mount (5 goals, 2 assists)#BURAVL pic.twitter.com/gj5ILCIXyX
And if he keeps performing to this level, surely he will have every chance of catching the eye of England boss Gareth Southgate ahead of Euro 2020.
Newcastle sat deep and pressed only in their defensive third against Leicester on Wednesday, but their game plan unravelled in three reckless minutes with two errors leading to goals before the break.
To compound Steve Bruce's woes, four quickfire injuries meant his side were forced to play with 10 men for 39 minutes, while DeAndre Yedlin also played on with a broken hand - and these are likely to prove far more costly than the result.
The Magpies now have 11 injured players - more than any other Premier League club - and Bruce was, justifiably, quick to take aim at the hectic festive schedule in his post-match comments.
Jetro Willems, Javier Manquillo, Jonjo Shelvey, Fabian Schar and Yedlin suffered knocks and join captain Jamaal Lascelles, Matt Ritchie, Paul Dummett, Ciaran Clark, Ki Sung-Yueng and Allan Saint-Maximin on the treatment table.
After an impressive bounce in form, Newcastle have now lost three successive games and their league-topping injury list could drag them back into the relegation dogfight they had valiantly escaped less than a month ago.
A mere 18 months after becoming Brighton's record signing, Alireza Jahanbakhsh is finally starting to repay some of that faith.
He was visibly emotional on the pitch on Saturday against Bournemouth when scoring his first goal for the club since joining for £17m from AZ Alkmaar in July 2018, and he opened up after the match explaining his struggles in adapting to life in the UK.
Well, his bedding-in period looks firmly behind him now after his moment of genius rescued an unlikely point for Brighton against Chelsea just when they looked out of ideas. Kepa Arrizabalaga could only watch as the Iranian's overhead kick left him stranded after Lewis Dunk had kept alive a corner from the right flank.
There had been reports that Jahanbakhsh might move away from Brighton on loan this month. I think the fans may riot if that move is sanctioned now. They have a new hero.
When Nigel Pearson was named Quique Sanchez Flores' successor at Watford on December 6 on a season-long deal, there were more than a few raised eyebrows at Vicarage Road.
However, the former Leicester manager has already had a galvanising impact in just the five Premier League games he has been in charge for, winning three of them and drawing another.
Not only that, but Wednesday's nerve-jangling 2-1 victory over Wolves was also the first time since last February the Hornets have recorded back-to-back league wins, an impressive run that has now seen Pearson's team move to within just a point of safety.
Defensive solidity will be on Daniel Farke's list of new year resolutions, but while his back-line was breached for a league-high 41st time, it was again a case of failing to convert more than one of the 15 chances they created in the 1-1 draw against Crystal Palace.
Farke has outlined a plan to target at least a point per game in the second half of the season, but the new decade has begun in the same vein as the old one ended: with a sense of two points dropped at Carrow Road.
"It feels like a loss," the German admitted afterwards with his side seven points adrift of safety.
Beset by injuries, Crystal Palace knew the importance of collecting something from their visit to East Anglia with Manchester City and Arsenal to face after their FA Cup third-round tie with Derby.
With a depleted squad, they have rallied after a tough spell in November - extending their spirited run to one defeat in eight league games to allow the Eagles to sit comfortably in the top half of the table.
Roy Hodgson has suffered a recent injury epidemic with several youth-team players named on the bench once more, and it was the 18-year-old Brandon Pierrick who played his part in his side's late leveller as Connor Wickham scored from close range - but Wilfried Zaha was again the focus of attention in his post-match press conference.
"He hasn't trained since the last game," the Palace boss said afterwards. "We were concerned he wouldn't get on the field but because he's got such a big heart for the club and such a love for football he declared himself fit."
Although faring well with limited resources, Hodgson has made no secret of the need to strengthen in January, but he knows it will be a long month battling to keep hold of his most-prized asset.
Eight defeats from 10 makes very grim reading for Bournemouth. They have been streaky as long as they have been in the Premier League but this downward spiral shows little sign of abating and has dropped them into the relegation zone. Eddie Howe looked a broken man on the touchline during his side's 4-0 battering at West Ham, and you couldn't blame him.
Injuries are still a big problem for Howe, but more worryingly, Bournemouth have precious little in the way of fight at the moment. They made life so easy for West Ham, surrendering possession in positions they couldn't afford to and had little in the way of ideas on the odd occasion they did get into the opposition half. They had only one shot in the first half at the London Stadium, made only one chance of note throughout the match, and have now lost eight out of their last 10 in the Premier League.
Howe has been through too much with Bournemouth to ever give up the fight. But it is tough to know where they go from here.