This has been one of the most memorable Champions League group stages in history, and Matchday Five will be a pivotal moment for several big clubs.
It could see the elimination of champions from England, Holland, Russia, Portugal, and Italy, while reigning champion Chelsea has a nerve-wracking away game to negotiate too. The previous Matchdays have provided late drama, superb goals, surprising shocks and stars of the future. Here are some storylines to watch from Matchday Five...
City faces Real Madrid at the Etihad and while the pre-match build-up to their Matchday One clash focused on the Roberto Mancini-Jose Mourinho rivalry, City's one-time flirtation with Cristiano Ronaldo (which may yet be rekindled, with the winger playing in Manchester this week for the first time since leaving United), and the Mario Balotelli sideshow, there is only one story this time around: fail to beat the Spanish champion, and City is out of the Champions League again.
Mancini has said "a miracle" is required for City to progress and he is right; City is winless in four and was fortunate to avoid defeat at home to Borussia Dortmund. And a reminder for any fans going: don't leave early. Three of City's group game matches have hinged on dramatic moments in injury-time (conceding a winner in Madrid, equalizing against Dortmund and failing to get a penalty against Ajax).
Chelsea also faces a tricky trip to Turin with Group E delicately poised. Group leader Shakhtar Donetsk is ahead of Chelsea on goal difference, both with seven points, with Juventus on six points. Tuesday's Chelsea-Juventus clash has a knock-out feel to it: if Juventus win, then Chelsea's fate will be out of its hands on Matchday Six; a draw or away win and the reigning champion should be fine.
Shakhtar must also beware. It has been on top for almost all of its games so far and still is at risk of not qualifying. For a team that dominated Chelsea as it did at Stamford Bridge -- and still ended up losing -- it would be a loss to the competition were it not to reach the Round of 16.
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On Matchday Four, Zlatan set up all four goals in PSG's 4-0 demolition of Dinamo Zagreb. With 18 goals in 19 games this season, and a win ratio of 68 per cent, Zlatan is on a streak right now -- and PSG needs him now. In Zlatan's absence, PSG drew to Montpellier and lost to a Rennes team that played with nine men for over half an hour.
Then again, was it such a surprise? Celtic had played a similar tactic on Matchday Three at Camp Nou, and was only undone by a last-minute winter from Jordi Alba. As many Celtic fans have since pointed out, over 180 minutes against Barcelona, it was only behind for one of them. Barcelona was dignified in defeat, with coach Tito Vilanova suggesting that his team would win a game like that 95 percent of the time. "We don't need a Plan B, we just need to make Plan A work better," said defender Dani Alves.
But Celtic's famous win, which has been ranked just behind the 1967 European Cup final victory over Inter Milan in its history, will be meaningless if the team fails to qualify from Group G. At the moment Celtic is three points clear of third-placed Benfica, to whom it travels on this week. A draw will as good as secure a place in the Round of 16, while a defeat would leave it needing to win the home tie against Spartak Moscow on Matchday Six. It could be a nervy night in Lisbon, though it has been lost on no-one that the Portuguese capital was also the scene for that 1967 success. The Lisbon Lions have become Lennon's Lions.
Giroud is likely to start for an Arsenal side needing to beat his former club Montpellier to keep its Group B fate in its own hands. Though the French champion is bottom of the pile and unable to progress, Giroud has warned that it can cause problems: "They have nothing to lose now they are already eliminated and you have to be careful, as that's when some teams are at their most dangerous: the pressure is off them. They didn't become champions of France with no talent."