While FC Bayern München and FC Barcelona sail along, that is in stark contrast to FC Schalke 04's recent run. UEFA.com looks at the form of the eight sides in action this week.
It is 75 days since the group stage ended and as well as tinkering with their squads, the last eight teams to return to the UEFA Champions League this week approach the round of 16 in contrasting shape.
Arsenal FC, FC Porto, AC Milan and Galatasaray AŞ are generally heading in the right direction while the domestic juggernauts of FC Bayern München and FC Barcelona show no sign of slowing down. It has all gone in the opposite direction for FC Schalke 04, with the Gelsenkirchen outfit stuck in a quagmire after one win in 12 matches. Málaga CF have hardly been lighting up Spain either.
After a strong finish to 2012, Arsenal struggled to get out of the blocks in the new year, managing just one win in five games in all competitions. A 5-1 victory over West Ham United FC on 23 January proved a turning point, the Gunners then winning four out of five, drawing the other. Tenth in the Premier League when they concluded their group stage campaign, Arsène Wenger's side now lie fifth but suffered a setback on Saturday: a 1-0 home defeat by second-tier Blackburn Rovers FC ending their FA Cup ambitions.
FC Bayern München
Jupp Heynckes's team have been irresistible, stretching their unbeaten run to 18 games in all competitions. Since a month-long winter break that included a training camp in Qatar, Bayern have won five out of five in 2013 and, with Bayer 04 Leverkusen faltering, sit 15 points clear at the head of the Bundesliga. The news that Heynckes will retire at the end of the season and be replaced by Josep Guardiola did not break their concentration. Mario Mandžukić has scored in each of his five matches for club and country this year, seven goals in all.
Vítor Pereira's side are 12 games unbeaten since losing at Paris Saint-Germain FC on 4 December, winning nine. They remain locked at the Liga summit with SL Benfica, after a 2-2 draw between them on 13 January, and the pair are on a collision course for the League Cup final after being kept apart in the draw for the last four. The goals continue to flow for Jackson Martínez, who has scored 20 in 19 top-flight appearances this term, though his effort was not enough to beat struggling SC Olhanense in their last home game – a 1-1 draw which ended Porto's 12-match winning streak in the Liga at the Estádio do Dragão.
Manuel Pellegrini's men have claimed just four victories in ten outings in 2013, though that has not prevented them rising to fourth in the Liga. The pre-Christmas highlight was a 3-2 home victory over Real Madrid CF on 22 December, but a draw was all they could muster in three meetings with FC Barcelona last month – two of them in the cup as Málaga's Copa del Rey hopes were terminated. There are problems at the back – the Boquerones had not kept a clean sheet in 11 games before shutting out Athletic Club on Saturday, yet Júlio Baptista's return after 16 months out with an Achilles problem provides an attacking fillip.
The Rossoneri have made steady progress up the Serie A table since the group stage closed, a run of seven wins in ten league matches lifting Massimiliano Allegri's team into the top five, from a position of 13th in mid-November. There has not been more than a goal in it in each of their seven fixtures in 2013 – including a 2-1 loss to Juventus in the Coppa Italia quarter-finals – but they have had the edge in the league, winning five and drawing two this year. Mario Balotelli has scored four of their last five goals, with the other an own goal, yet they will have to fare without him in Europe.
Barcelona have extended their Liga lead over second-placed Club Atlético de Madrid from six points into double figures. Lionel Messi has, as ever, been at the heart of the procession, and has scored in a record 14 consecutive Liga games, surpassing the previous mark of ten. The Catalan giants have not had it all their own way, however, as their unbeaten start to the top-flight campaign – comprising 18 wins and one draw – ended on 19 January when Real Sociedad de Fútbol came from two down to beat them 3-2 in San Sebastian.
Galatasaray have had a mixed time since rounding off their group campaign, a return of five wins in eight Super League games not preventing them building a five-point advantage at the summit – they led on goal difference at the start of December. There was disappointment in the Turkish Cup, however, where their aspirations were ended by second-tier 1461 Trabzon on 11 December. Didier Drogba scored five minutes into his debut on Friday and the partnership between Umut Bulut and Burak Yılmaz remains as prolific as ever – the pair have scored 32 of Galatasaray's 57 goals in all competitions this term.
FC Schalke 04
The Gelsenkirchen outfit have had a torrid time since matchday six of the group stage, losing five out of eight matches on all fronts. Coach Huub Stevens departed on 16 December, with Jens Keller taking up the reins until the end of the season. Schalke's German Cup bid was halted by 1. FSV Mainz 05 in his first game in charge but, after a month-long winter break that included eight days in Qatar, they began 2013 with a stunning 5-4 victory over Hannover 96. That provided only brief respite and Schalke travel to Turkey having produced just one win in their last 12 fixtures.