Holders Bayern Munich begin their Champions League defence with the visit of Atletico Madrid on Wednesday, in a game that will pit Robert Lewandowski against Luis Suarez.
Liverpool, winners in 2019, travel to Ajax, and Real Madrid host Shakhtar Donetsk, with two of the competition's most successful clubs hoping to avoid some worrying runs of defeats.
Antonio Conte's Inter tackle Borussia Monchengladbach and Manchester City host Porto, a team who boast a rather unfortunate record when it comes to games on English soil.
Here is some of the key Opta data from day two of matchday one.
Ajax v Liverpool: Can Firmino stop the rot?
This will be Liverpool's first meeting with Ajax since the 1966-67 European Cup, when the Dutch side prevailed 7-3 on aggregate in the last 16.
Liverpool's campaign last season ended at the same stage with back-to-back losses to Atletico Madrid. Should they lose in Amsterdam, it will be the first time since Brendan Rodgers was in charge in October to November 2014 that they have suffered three consecutive Champions League defeats.
Perhaps Roberto Firmino is the man to help them. He has been directly involved in 26 goals (15 scored, 11 assisted) in 33 Champions League matches; since his debut in 2017-18, the only other player with 10 or more goals and assists in that time is Kylian Mbappe (13 goals, 13 assists).
Bayern Munich v Atletico Madrid: Lewandowski has history in his sights
Bayern were the first team in history to win every game en route to lifting the trophy last season, and their 11-game winning run is already the longest ever in the competition.
Should Robert Lewandowski score, he will become the first player to do so in 10 Champions League group games in a row. He currently shares the record of nine with Cristiano Ronaldo, who did so from 2012 to 2014.
Atletico have only won twice in their previous 10 group games away from home, but Luis Suarez could give them the boost they need – he has scored five goals in his last five starts in the competition, as many as he managed in his previous 31 starts combined.
Real Madrid v Shakhtar Donetsk: Zidane puts 100 per cent record on the line
Real Madrid have been in the Champions League group stage 28 times and have never failed to reach the next round. Leeds United, who did so twice, are the only other team to feature in more than one group stage and boast a 100 per cent record.
That said, Madrid lost their final two games last season – both legs of the last-16 tie with Manchester City – and losing to Shakhtar Donetsk would put them on a three-match losing streak in the Champions League or European Cup for the first time since September 1986.
With captain Sergio Ramos injured, Zinedine Zidane will have concerns about his defence. At least the forward line is in capable hands: Karim Benzema has managed four goals and two assists across six consecutive home games in the competition, and Shakhtar have failed to keep a clean sheet in 22 Champions League matches in a row.
Manchester City v Porto: More English misery?
Porto have played 20 away games against English sides in Europe and have failed to win any. In fact, they have lost 17 of those games and have not scored in the previous seven. They do at least go into this contest off a run of just two defeats in 16 Champions League group-stage matches.
City have a pretty strong recent record in the group stage, having gone unbeaten in 11 games since a surprise 2-1 loss to Lyon in September 2018. They also have Raheem Sterling in sharp form: the forward has scored 20 goals in the competition since his debut for City in September 2015, a tally only Harry Kane can match among English players in that time.
Inter v Borussia Monchengladbach:
9 – Romelu Lukaku has scored nine goals in 11 appearances in European competition for Inter. Since the start of last season, only Robert Lewandowski (15) and Erling Haaland (10) have netted more across the Champions League and Europa League.
8 – Strike partner Lautaro Martinez has scored five in six Champions League starts and eight in 14 in Europe overall for the Nerazzurri.
Salzburg v Lokomotiv Moscow:
10 – Since September 2018, Lokomotiv Moscow have lost 10 Champions League games, more than any other club in that time.
16 – Salzburg scored 16 group-stage goals last season but finished third in their group. The only other team to score that many and get knocked out were Chelsea in 2012-13.
Midtjylland v Atalanta:
16 – Atalanta have scored at least once in 16 of their previous 17 European games, including nine in three matches in last season's knockouts. Josip Ilicic has nine goals in 13 European appearances for the club.
18 – Midtjylland conceded 18 goals in eight matches in the 2015-16 Europa League, their previous involvement in Europe. No team conceded more that season.
Olympiacos v Marseille:
3 – This will be Andre Villas-Boas' first Champions League game since March 2016. He has lost his most recent three matches in the competition.
41 – Steve Mandanda has made 41 appearances in the competition, the most for any Marseille player in history. The goalkeeper accounts for 37 per cent of the total games played by current Marseille players in this tournament.