What to watch: Champions League matchday two

Barça under the microscope
The European champions have shipped four goals in three of their nine games this season; they have kept just two clean sheets and have conceded 17 in total – a figure they did not reach until 28 January last term. Luis Enrique's pre-season warning – "we talked about defence but it hasn't helped, so we'll have to improve again" – does not appear to have been heeded and becomes even more important following Lionel Messi's injury.
Barcelona v Leverkusen – Tuesday

Juve's slow start
Last season's runners-up have been especially slow out of the traps. Six matches into their Serie A title defence and with only five points on the board, Juventus are well off the pace. The matchday one victory at Manchester City briefly steadied the ship, but UEFA Europa League holders Sevilla may nevertheless fancy their chances in Turin after finally winning a Liga match on Saturday. "Juve will always have a special place in my heart," said Sevilla's former Bianconeri striker Fernando Llorente.
Juventus v Sevilla – Wednesday

Mourinho's Porto return
José Mourinho made his name at the Estádio do Dragão and returns there with a Chelsea side who have won their last eight meetings with Portuguese opposition. Mourinho also took the west Londoners back to his old stomping ground in the 2004/05 group stage – the first season of his maiden spell at Stamford Bridge – and the visitors lost 2-1.

Casillas eyes record
Mourinho will be reunited in Porto with Iker Casillas, with whom he worked for three seasons at Real Madrid. The Spain goalkeeper racked up 150 UEFA Champions League outings – group stage to final – while in the Spanish capital and added one more with his new employers on matchday one. He is now set to reach 152, a milestone which will take him past Xavi Hernández and create a new competition record.
Porto v Chelsea – Tuesday

Ronaldo chasing Raúl 
Cristiano Ronaldo is just three shy of passing Raúl González's 323-goal record to become Real Madrid's all-time leading scorer. Even for a talismanic player with as many records to his name as Ronaldo, this – in little over six seasons – would be a real feather in his cap. Malmö could be the unfortunate victims.
Malmö v Madrid – Wednesday

Dinamo Zagreb – 45 and counting
Dinamo Zagreb have not lost in 45 games in all competitions, a sequence dating back to 27 November last year and a 1-0 reverse to Astra Giurgiu in the UEFA Europa League group stage. Arsenal provided a real threat to this run on matchday one – a hurdle cleared in emphatic fashion – but Bayern München in Germany will surely be Dinamo's sternest test yet.
Bayern v Dinamo – Tuesday

Astana's home bow
Wednesday will mark the first ever UEFA Champions League group stage match to be held in Kazakhstan. The visitors to Astana will be Galatasaray, no strangers to high-octane atmospheres in Europe but themselves seeking a first away victory in the competition since March 2013.
Astana v Galatasaray – Wednesday

Gladbach's caretaker
Borussia Mönchengladbach's caretaker coach André Schubert has enjoyed a fine start to life after Lucien Favre, who had presided over six straight defeats. Gladbach were 4-0 up against Augsburg inside 21 minutes in midweek – eventually winning 4-2 – and on Saturday won 3-1 at Stuttgart, and now face a City team whose form has suddenly taken a turn for the worse. "The entire club is looking forward to this game," said Schubert. "It would be a sensational achievement to get through such a difficult group."
Gladbach v City – Wednesday

Olympiacos's woes in England
The Greek champions will hardly have been jumping for joy when pitted against Arsenal in Group F. The sides are in the same section for the fourth time in seven seasons, and though Olympiacos have won their three most recent home matches against the Gunners, their record in north London and beyond leaves a lot to be desired. Indeed they have lost on each of their last 12 visits to England, letting in 37 goals and scoring only three.
Arsenal v Olympiacos – Tuesday

Clinical Cavani
Paris striker Edinson Cavani is in lethal form, registering 21 goals in his last 21 club appearances, coming off the bench to score against Nantes on Saturday. Any notion Shakhtar may have had of merely needing to keep Zlatan Ibrahimović quiet will surely have been dispelled by the Uruguay ace's sensational streak. "I feel great and need to keep doing the same," said Cavani.
Shakhtar v Paris – Wednesday