AFP Sports previews Tuesday's eight games on matchday four:
Both these sides suffered league defeats at the weekend -- Shakhtar going down 2-0 at Volyn Lutsk, which was the third defeat on the road for Mircea Lucescu's men, while Leverkusen were embarrassed 1-0 by rock-bottom Eintracht Braunschweig to fall four points behind Bayern Munich.
Leverkusen's fit-again Lars Bender, who signed a contract extension in midweek, received a late red card for his second bookable offence while Stefan Kiessling, Sidney Sam and Heung-Min Son were all on the bench at the start.
The Germans won the first tie between the two sides last month, a comprehensive 4-0 home win which put them on six points, one behind Manchester United.
Shakhtar, who were quarter-finalists in 2011, have not beaten a German side at home in Europe since seeing off Eintracht Frankfurt in the 1980/81 UEFA Cup.
United can virtually ensure their last 16 place with victory in Spain after a 1-0 home win over Sociedad, playing in the tournament for the first time in 10 years, in Manchester moved them onto seven points from three games.
But David Moyes's side have doubts over the fitness of Jonny Evans, Rafael da Silva and Tom Cleverley, who were all replaced at half-time in Saturday's 3-1 win at Fulham.
"It will be a difficult test against (Real) Sociedad," said Moyes.
"To go and play against any side in Spain who have qualified will be a hard test, but we will go over there and try and get a good result that will continue our good form in the group."
Sociedad have scored just once in three Champions League games so far and are without a point but warnmed up for Tuesday with a confidence-boosting 5-0 home win over Osasuna.
Jagoba Arrasate's side are looking to avoid setting a club-record sequence of four straight defeats in Europe.
Real Madrid have nine points from three games after a Cristiano Ronaldo double ensured a 2-1 win over Juventus last time out and they need just a point in Turin to make sure of a last-16 place.
Nine-time winners Madrid have scored in all their last 19 Champions League away fixtures, losing only four but Juventus have won the last five meetings between the sides in Turin.
Juventus are in third place and with that position in mind coach Antonio Conte rested Andrea Pirlo in Saturday's 1-0 win at Parma before the veteran midfielder replaced Claudio Marchisio.
Ronaldo has scored seven times for Real Madrid in the Champions League this season just one off the record held jointly by Ruud van Nistelrooy, Filippo Inzaghi and Hernan Crespo.
On Saturday, Real beat Rayo Vallecano 3-2 with a Ronaldo double and a Karim Benzema header as Gareth Bale laid on two goals for the second consecutive game.
Real will be without left-back Fabio Coentrao after he limped off with an ankle injury. Xabi Alonso is also a doubt but Raphael Varane will return at the heart of the defence after being rested against Rayo.
Galatasaray won the first match 3-1 in Istanbul to put themselves in second spot in the table, five points behind Real but two ahead of Juve and three up on Copenhagen.
The Danes drew 1-1 with Juve and lost 4-0 at Real Madrid while Galatasaray recovered from their opening 6-1 drubbing to the Spaniards to draw 2-2 with Juventus in Roberto Mancini's first game as coach.
Copenhagen's home record in the tournament gives some cause for optimism -- in eight matches, they have lost only to Chelsea and have beaten Manchester United and drawn with Barcelona in previous years.
For Galatasaray, Copenhagen holds special memories -- in 2000, a Fatih Terim-led team overcame Arsenal on penalties in the UEFA Cup final.
The French side can qualify for the knockout stages for the second successive year with victory over an Anderlecht team they walloped 5-0 in their previous encounter a fortnight ago to make it three impressive wins from three games in an admittedly easy group.
The only good news for Anderlecht is that there are doubts over whether Swedish star Zlatan Ibrahimovic, who scored four in the first match, will be fit as he was rested for the 4-0 Ligue 1 win over Lorient last Friday -- extending PSG's unbeaten Ligue 1 run to 23 -- with an inflamed knee.
Anderlecht are searching for their first point and first goal of the campaign while their last away win in the Champions League came in the 2005/06 season at Real Betis.
A lot at stake in this match as with both on four points, and Anderlecht on zero, they are battling for the runners up spot and a place in the last 16 or the third-place finish that guarantees a spot in the Europa League knockout stage, a competition in which the Portuguese outfit reached the final last season only to lose to Chelsea.
The sides drew 1-1 in Lisbon, and Olympiakos will be looking to repeat their 5-1 win the last time they hosted Benfica in the Champions League in the 2008/09 campaign.
Three Benfica players remain from that thumping including striker Oscar Cardozo, who was only on the bench that night but will be hoping to lead the line on Tuesday. Similarly Kostas Mitroglou should be up front for the hosts and eager to add to his tally of goals, having earlier this term become the first Greek player to score a hat-trick in the Champions League, admittedly against the porous Anderlecht defence.
City made heavy weather of beating the Russian outfit a fortnight ago in a match overshadowed by a racism controversy but look in sharper form after a 7-0 demolition of Norwich on Saturday, their biggest win in the top flight since 1968.
Victory over the Russians would all but assure them of reaching the knockout stages for the first time after two flops under Roberto Mancini.
The Italian's successor, Chilean Manuel Pellegrini showed his ruthless side when he dropped Joe Hart from the Norwich game and Romanian Costel Pantilimon may well keep his place for the CSKA game.
City's talismanic central defender and captain Vincent Kompany is still struggling with a thigh injury and missed the Norwich game. CSKA come into the game on the back of a come from behind 2-1 win over Volga with impressive Ivorian striker Seydou Dumbia on the scoresheet.
The Germans are proving as unbeatable as PSG are, their 2-1 win over Hoffenheim on Saturday equalling the Bundesliga record for the longest unbeaten run, levelling the 36 matches unbeaten Hamburg achieved between January 1982 and January 1983.
Victory on Tuesday, and CSKA failing to win at City, will see the holders qualify for the last 16.
However, not all is rosy in the Munich camp as they are still struggling to impose themselves early in their matches.
"Obviously it's not such a wonderful situation," said Mario Goetze, who caused Pilsen all sorts of problems once he came on in the second-half of their match a fortnight ago, which ended in an easy 5-0 win for the German side.
Pilsen have an impressive home record in the competition winning 10 out of 11 before City beat them this season.
Bayern, though, are closing in on their record of successive away wins in the competition, six on their way to winning the 1996 title, as victory on Tuesday would be their fifth in a row.