UEFA.com has the key statistics about matchday four, including FC Bayern München's winning run and contrasting records for Club Atlético de Madrid and Real Sociedad de Fútbol.
Group A (Real Sociedad de Fútbol v Manchester United FC, FC Shakhtar Donetsk v Bayer 04 Leverkusen)
• United have not won away in Europe since a victory at SC Braga on 7 November last year. Jagoba Arrasate's La Real are looking to avoid setting a club-record sequence of four straight defeats in Europe.
• Shakhtar's last home success over Bundesliga opposition came against Eintracht Frankfurt in the 1980/81 UEFA Cup first round when Mikhail Sokolovski earned them a 1-0 first-leg win, although the ensuing 3-0 loss in Germany meant it was in vain. Leverkusen went down 2-0 in Ukraine last November at FC Metalist Kharkiv in the UEFA Europa League group stage.
Group B (Juventus v Real Madrid CF, FC København v Galatasaray AŞ)
• Juventus have won the last five meetings between the sides in Turin – in the other encounter in northern Italy, the first between the teams, Madrid triumphed 1-0 in a 1961/62 European Champion Clubs' Cup quarter-final first leg.
• Galatasaray have lost just three of their last 20 European away fixtures, winning ten.
Group C (Paris Saint-Germain FC v RSC Anderlecht, Olympiacos FC v SL Benfica)
• While PSG have scored 12 times and conceded only once in winning their first three games, Anderlecht have shipped ten goals and are still waiting for their first goal and point.
• Olympiacos and Benfica met in Piraeus in the 2008/09 UEFA Cup group stage, the Greek side prevailing 5-1.
Group D (FC Viktoria Plzeň v FC Bayern München, Manchester City FC v PFC CSKA Moskva)
• Although Plzeň lost at home to Manchester City on matchday one, they had won ten of their preceding 11 home fixtures in UEFA competition. Bayern are enjoying their best run of form on the road in Europe since posting six straight away victories in their triumphant 1995/96 UEFA Cup campaign. Including last season, they have won four in a row in the UEFA Champions League – and five of their last six.
• This is City's first home encounter with Russian opposition while CSKA have visited England four times in the past decade – earning a draw on three of those trips, most recently 3-3 at Manchester United in the group stage on 3 November 2009.
Group E (Chelsea FC v FC Schalke 04, FC Basel 1893 v FC Steaua Bucureşti)
• Chelsea have recorded five victories and a draw at home to German opponents. Schalke won 2-0 in London against Arsenal FC in last season's group stage but that was their first success on English soil after a draw and four defeats.
• Basel have won two of their three home games against Romanian clubs, but lost the last one. Steaua drew on their first two visits to Switzerland, before being beaten on their two most recent trips.
Group F (Borussia Dortmund v Arsenal FC, SSC Napoli v Olympique de Marseille)
• Dortmund, who are chasing their eighth straight home victory in the UEFA Champions League, have never lost on their own ground to English teams, winning four of the seven contests. Arsenal are unbeaten in their last four away games in Germany.
• Before matchday three and their 2-1 triumph at Marseille, Napoli had scored only two goals in six games with Ligue 1 clubs. OM went down 2-1 at FC Internazionale Milano in the 2011/12 round of 16 – their first reverse in Italy in four matches – but went through on away goals after a 1-0 home win.
Group G (Club Atlético de Madrid v FK Austria Wien, FC Zenit v FC Porto)
• Atlético will qualify for the knockout rounds for the first time since 2008/09 with another victory and will also set a club record for consecutive wins in Europe's elite competition. Prior to this season their best sequence was three straight victories, posted in their inaugural European Champion Clubs' Cup campaign of 1958/59.
• Porto's away record against Russian sides is W4 D0 L1. Zenit have already won at home to one Portuguese team this term, having seen off FC Paços de Ferreira 4-2 in the second leg of their UEFA Champions League play-off to complete an 8-3 triumph. Moreover, they have never lost at home to visitors from Portugal, their stats reading W4 D1 L0 – including a 3-1 defeat of Porto in the 2011/12 group stage.
Group H (FC Barcelona v AC Milan, AFC Ajax v Celtic FC)
• The 3-0 semi-final home loss to Bayern in May is Barcelona's sole reverse in their last 23 UEFA Champions League home fixtures. Milan lost twice in Spain last season, going down 1-0 at Málaga CF in the group stage in addition to their 4-0 defeat at Barcelona in the round of 16 second leg; they have not won on any of their last five visits to the country.
• Ajax have won just three of their last ten matches in UEFA competition in Amsterdam, losing five. Celtic hope to avoid a third successive European away defeat this season.