With the season at its halfway point, it's time to take stock of how clubs across Europe are getting on.
ESPN FC's club correspondents across all the major European leagues grade the team's season so far, pick a star man, flop, key question and predict the rest of the campaign.
Ernesto Valverde has brilliantly steadied the ship since the Super Cup defeat to Real Madrid. To have Barcelona nine points clear at Christmas, safely through in the Champions League and 25 games unbeaten in all competitions is a wonderful achievement.
Star man: There are several candidates. Lionel Messi is the obvious, predictable one, while Paulinho, a much-maligned summer signing, is a more left-field option. Samuel Umtiti also deserves a mention but the plaudits go to goalkeeper Marc-Andre ter Stegen, whose improvement this season has been remarkable -- and fundamental to Barca's success.
Flop: There were doubts about Gerard Deulofeu when he returned from Everton for €12 million in the summer. Had he matured? Was he ready for Barca's first team? The answer, so far, is no. Even with Ousmane Dembele's injury creating the perfect chance for him to impress.
Key question: Will Dembele's return make Barca even better or could it rock the balance they've established?
Prediction: La Liga: 1st. Spanish Cup: Runners-up. Champions League: Semifinal. -- Sam Marsden
REAL MADRID: D
Victories in two Super Cups and the Club World Cup cannot mask that 14 points off the pace in La Liga and a second place qualification in the Champions League is just not good enough.
Star man: While many of Madrid's Galacticos including Cristiano Ronaldo have had inconsistent seasons so far, Isco's form has held up pretty well, and his absence from the 3-0 Clasico disaster before the winter break only enhanced his reputation with Blancos fans and pundits.
Flop: Karim Benzema took the most flak through the autumn months, as he missed chance after chance. He has hit the woodwork more times (six) than the back of the net (five) in all competitions.
Key question: Will club president Florentino Perez look to strengthen in January, with the realistic focus now switching to the cup competitions? The pain of the Clasico defeat will require a reaction of some sort -- and shaking up the squad by adding a new top defender and striker could help to recharge Real Madrid's season.
Prediction: 3rd. Spanish Cup: Semifinals. Champions League: Runners-up. -- Dermot Corrigan
ATLETICO MADRID: B
Just one defeat in La Liga and the nearest challengers to Barcelona would usually be cause for celebration -- however the disastrous Champions League campaign means it is a B for Diego Simeone's boys thus far.
Star man: Jan Oblak. At the heart of Spain's second-meanest defence, he has already racked up 10 clean sheets in La Liga and conceded more than one goal just once. The brilliant Slovenian was one of the few to come out of the Champions League shambles with his head held high, too.
Flop: Yannick Carrasco. Has lost his place in the team and is without a goal since September. Luciano Vietto and Nicolas Gaitan deserve special mentions, too.
Key question: Is Antoine Griezmann's head in the right place? If Atleti can ensure he remains fully committed to the cause for the rest of the season, with Diego Costa's return imminent, they have serious potential to kick on and achieve something special this season. However, if he sulks and mopes, Simeone has a big decision to make about his place in the side.
Prediction: La Liga: 2nd. Spanish Cup: Runners-up. Europa League: Winners. -- Joe Walker
For a team that started the season poorly, Juventus have done well to catch up in Serie A, with only a point separating them and Napoli in first place. They also sealed qualification for the latter stages of the Champions League.
Star man: While both Medhi Benatia and Douglas Costa have impressed, Blaise Matuidi is the star man for having integrated himself within the side and Massimiliano Allegri's tactical schemes quickly. Providing energy, physicality and a constant dynamic presence from his first appearance in the Bianconeri jersey, Matuidi has really helped the side to fight until the end and achieve balance in midfield.
Flop: For a full-back who thrilled the world with his performances last season, generating a lot of interest in the transfer market, Alex Sandro has experienced a great decline this term. Struggling to replicate his outstanding form, the Brazilian is slowly improving but will need to do much more to earn back the admiration he once had from the coach and the fans.
Key question: Can Juve find the right balance in attack? A lot of money has been invested in this forward line to ensure they are a constant threat going forward but we are yet to see Paulo Dybala play to his potential.
Prediction: Serie A: 1st. Italian Cup: Winners. Champions League: Semifinals. -- Mina Rzouki
INTER MILAN: A
Leading Serie A recently was a sign of Luciano Spalletti's success in undertaking a major job. He ensured Ivan Perisic was not sold and brought in Milan Skriniar, Borja Valero and Matias Vecino: not the kind of names to appease the fans' fears, but given their performances (compared to AC Milan's 11 new signings...), it was certainly a case of quality over quantity. Spalletti has done a fine job.
Star man: Mauro Icardi. The Argentinian has managed to win over the dissenting Inter fans who declared him unworthy of wearing their shirt after he criticised them in his autobiography just over a year ago. His 17 goals in 18 Serie A matches have helped Inter to 25 points from the 10 games in which he has scored; only against Udinese was his goal in vain.
Flop: Dalbert has hardly delivered on his promise. He has been relegated to the bench with Yuto Nagatomo and Davide Santon preferred by Spalletti.
Key question: Every side suffers a blip in a season and how long Inter's will last will be a measure of how serious their title challenge is.
Prediction: Serie A: 4th. Italian Cup: Runners-up. -- Ben Gladwell
Napoli's Champions League disappointment stands out like a saw thumb compared to what has otherwise been an outstanding season for Maurizio Sarri's men.
Star man: Lorenzo Insigne. He just edges out Dries Mertens, who may have scored more (13) and provided more assists (five), but is actually performing below the standards he set last season. Insigne, on the other hand, is maturing into the finished product.
Flop: Mario Rui. A serious injury to Faouzi Ghoulam, who had been winning over plenty of admirers for his early-season form, was an opportunity for Mario Rui. He didn't take it.
Key question: Sarri still has a threadbare squad which still has European football -- indeed an extra round of it following their demotion into the Europa League -- to cope with. Can they balance the two?
Prediction: Serie A: 1st. Italian Cup: Semifinals. Europa League: Semifinals. -- Ben Gladwell
Three defeats to direct title rivals show they have some way to go in Serie A but qualifying from a Champions League group that contained Chelsea and Atletico Madrid was some achievement.
Star man: Aleksandar Kolarov. The Serb has been a sensational addition to the squad since arriving from Manchester City and has fully won over fans who had suspicions over his Lazio past. Two goals and three assists from left-back, as well as winning penalty in the recent Rome derby victory, has been more than enough to do that.
Flop: It's probably unfair in both case, but both Patrick Schick and Rick Karsdorp have spent more time on the treatment table than they have on the pitch. While Schick looks to be warming up after months out, you look at the €40 million price tag, and what Mohamed Salah is doing at Liverpool, and wonder what might have been.
Key question: Roma have spent much of the season switching between being a thrilling team to watch and deeply frustrating one, with Saturday's 1-0 defeat to Juventus showing both of those traits. For 70 minutes Roma were solid but blunt going forward; then, for the final 20, they suddenly looked like a team capable of doing Juve some serious damage. Whichever one of those teams comes out in the second half of the season will be crucial in deciding how far Roma go.
Predictions: A quarterfinal exit in the Champions League after beating Shakhtar Donetsk in the round of 16, while anything better than third or fourth place in Serie A would be a huge result. -- Terry Daley
AC MILAN: D
With the investment over the summer firmly in mind, having been cut adrift of the top four already with Serie A leaders and rivals Inter being so far ahead, it's simply well below expectations and not good enough.
Star man: Alessio Romagnoli, Ricardo Rodriguez, Fabio Borini and Patrick Cutrone all came into consideration, but it's difficult to snub Suso for this one. The Spaniard still struggles with inconsistency, but with seven goals and seven assists in 23 appearances in all competitions, he has been the most decisive figure for Milan so far this season.
Flop: Lucas Biglia has been poor, while Hakan Calhanoglu is fortunate to miss out, albeit he has shown glimpses of his class. However, Nikola Kalinic has struggled badly this season and regularly faces jeers from the San Siro faithful. A lack of goals and little contribution to the build up of play has ensured he's been very disappointing.
Key question: Gennaro Gattuso appears to have found the biggest solution required having ditched the three-man defence and returned to a 4-3-3. Can he pair quality football and positive results with the grit and determination that he can naturally impart on the squad?
Prediction: Serie A: 6th. Coppa Italia: Semifinals. Europa League: Semifinals.
The Rossoneri need more from many of the summer signings, and it will be down to Gattuso to get that out of them to ensure his side make up ground in the race to qualify for Europe next season. -- Sumeet Paul
BAYERN MUNICH: A-
After a sluggish start to the season under Carlo Ancelotti, Bayern head into the New Year revitalised with strong chances in three competitions.
Star man: Jupp Heynckes has transformed Bayern's fortunes with 15 wins in 16 games in his fourth spell in charge.
Flop: Renato Sanches continues to struggle on loan at Swansea but the Portuguese starlet is currently out of sight, out of mind in Wales. So if we are being harsh and for want of any obvious candidates, Franck Ribery's illustrious career is inevitably drawing to a close at 34 -- but Bayern's longest serving player is quietly enduring another injury-ravaged campaign with no assists nor any goals in 11 Bundesliga and Champions League appearances.
Key question: Who succeeds the magisterial Heynckes in the summer is the key issue. Bayern already had the luxury of having Pep Guardiola lined up when "Don Jupp" was previously asked to step aside after his historic 2013 treble. No one of that calibre is waiting in the wings this time around. Thomas Tuchel remains a strong favourite to take over but president Uli Hoeness apparently has reservations about hiring the cranky ex-Borussia Dortmund coach. Julian Nagelsmann also looked a real contender but the 30-year-old's stock has fallen this season at Hoffenheim.
Prediction: Bundesliga: 1st. German Cup: Winners. Champions League: Semifinals. -- Mark Lovell
BORUSSIA DORTMUND: D+
Dortmund came flying out of the gates under Peter Bosz but ultimately crashed and burned in Bundesliga and Champions League.
Star man: Mario Gotze. Until picking up an ankle injury, Gotze was the bright spot although not being flashy with goals and assists. The 25-year-old brought structure to a chaotic midfield and has shown he can be a key cog in Dortmund's future.
Flop: Bosz. The coach was tasked to right the ship after BVB's ugly divorce with Tuchel. Bosz's non-stop, aggressive approach worked only until Bundesliga teams caught on to his tactics and not at all in the Champions League. After an unprecedented freefall from first to eighth place in the table, the Dutchman left a team completely drained of confidence.
Key question: Dortmund boast the best attack in the league after 17 rounds, scoring 39 goals. Can Peter Stoger steady a shaky defence in the second half of the season? If so, BVB will flourish again.
Prediction: Bundesliga: 2nd. Europa League: Runners-up. -- Stefan Buczko
PARIS SAINT-GERMAIN: A-
Overall, a very good start to the season with PSG nine points clear at the Ligue 1 summit, into the Champions League latter stages as group winners and into the quarterfinals of the Coupe de la Ligue.
Star man: Although there are a few candidates for this, Edinson Cavani has arguably been the most consistent performer. Neymar and Kylian Mbappe have had their moments and all three combine to form an absolutely lethal strike force but the Uruguay international, with his 25 goals and three assists from 25 appearances across all competitions, is the pick.
Flop: There are a few players in the running for this but Layvin Kurzawa has arguably been the most disappointing member of Unai Emery's regular starting XI so far this campaign. The France international has not been the same player since he underwent surgery on a groin problem last term and is a long way short of his impressive early form under the Spaniard.
Key question: The main issues PSG face over the second half of the season are how they will tackle their own complacency at certain moments, whether or not Thiago Motta's return to fitness solves the team's midfield issues and whether Emery can find a way to make the defence more balanced.
Prediction: Ligue 1: 1st. Coupe de la Ligue: Winners. Coupe de France: Winners. Champions League: Semifinals. -- Jonathan Johnson