On a night of Champions League drama, Arsenal took control of the Group of Death with a stunning win in Germany, while Lionel Messi ended his scoring drought for Barcelona. Elsewhere, Atletico Madrid reached the next round, while Chelsea took control of Group E.
Here are the main storylines from a cracking round of action:
Arsenal stuns the Yellow Wall in Germany
Arsenal stunned Borussia Dortmund with a smash-and-grab 1-0 win in Western Germany to leave the Gunners on the verge of qualifying for the Champions League Round of 16. Arsenal's man-of-the-moment Aaron Ramsey scored with Arsenal's first effort on goal, after 62 minutes, and the Gunners now join Napoli, a 3-2 winner over Marseille, as joint-leaders of the vaunted Group F with two games left to play.
Arsenal fans will look at this as a virtuoso away performance, but for the first hour, the club was just trying to survive. Dortmund had the better of a scrappy first-half, in which Arsenal's attacking players barely had a kick, but the hosts rarely tested Wojciech Szczesny in the visitors' goal. Henrikh Mkhitaryan came closest but his shot went just wide of the post.
The second half was a different story, as Dortmund twice had the ball in the net, but both times a goal was ruled out, correctly, for offside. As Dortmund's Yellow Wall of fans chanted their team on, Sokratis inexplicably gave the ball away, Mesut Ozil crossed, and Olivier Giroud brilliantly stretched his neck muscles to set up Ramsey who headed home from close range.
Dortmund pushed for an equalizer, playing coach Jurgen Klopp's preferred 'heavy metal' style of football, and gaps opened up at the other end as Ramsey almost doubled the lead, though Roman Weidenfeller did well to block his shot form close range. But Dortmund continued to create chances, mostly from the right: Marco Reus was guilty of one miss, swinging and missing the ball from four yards after a fizzing Robert Lewandowski cross. That led Mats Hummels, watching in the stands, to pull down his beanie hat over his eyes.
Arsenal looked more comfortable as the game went on; the tempo of Dortmund's impressive pressing faded, inevitably, and frustration grew. Penalty appeals were more desperate; shots flew in from increasing distances. Per Mertesacker was heroic in defense, with Germany coaches watching.
And so Arsenal held on and last season's runners-up face a battle to survive in the competition. Dortmund plays Napoli at home and Marseille away next. Arsenal has Marseille home and Napoli away. This group could still go down to the wire, but the English team is in pole position to progress.
One power faces a crisis, but it's not Barcelona
Despite the moans from Barcelona, the stories of crisis and Lionel Messi's reported scoring drought (which is only three consecutive games, as he scored against Milan two weeks ago), the facts of Barcelona's season are this: The Blaugrana are unbeaten in 18 games this season, have 10 clean sheets and their 3-1 win over AC Milan confirmed the club's place in the knockout round of this competition.
OK, so Barca did not dominate its opponent in the manner of Barcelona at its best under Pep Guardiola, but new coach Tata Martino is guiding a team in transition. Even though Messi has scored 14 goals in 15 games this season (four in five in Europe), the team is less Messi-dependent, in part due to Neymar's speedy integration, and also down to Alexis's improved form.
And yet it was Messi who will take the headlines: he scored an early penalty after Neymar was brought down, and then slotted home late on after Cesc Fabregas's brilliant one-two to double his tally and put the seal on a 3-1 win. Maybe it will be forgotten that minutes before that goal, Nigel de Jong had outpaced him to a long ball over the top.
In fact, the real crisis is in Milan, which briefly threatened after Kaka's cross was turned in by Gerard Pique before halftime. Instead, Milan coach Max Allegri will be fearing a knock on his door: with three league wins this season, Milan is closer in points to the relegation zone than the top four, and though it has not been helped by injuries to the likes of Giampaolo Pazzini and Stephan El- Shaarawy, and a shambolic recruitment plan overseen by Adriano Galliani, Allegri's time could be up.
His three seasons in Milan have finished first, second and third -- but even with this squad, fourth place looks a stretch. Italian broadcasters made much of the sight of president's daughter Barbara Berlusconi chatting with youth team coach Pippo Inzaghi before the game. Inzaghi is one of those being touted for Allegri's position, as is Clarence Seedorf.
Either way, if Allegri goes he can do so with his head held high. His record in Milan stands up to scrutiny and there is little shame in losing at Barcelona.
Dark-horse Basel ekes out point ahead of Chelsea rematch
What has happened to the FC Basel side that stunned Chelsea on Matchday One with a victory at Stamford Bridge? A team that looked like becoming the hipsters' dark horse has since lost at home to Schalke and needed a last-minute equalizer to scrape a 1-1 draw at home to Steaua Bucharest, who is now 20 games without a win in the competition.
Sio's late effort spared some Swiss blushes and it won't get any easier for Basel, which faces Chelsea next. The West London side, with six changes from the team that lost to Newcastle at the weekend, coasted to a 3-0 win over Schalke in front of Rafa Nadal, with goals from Samuel Eto'o (two) and Demba Ba.
Eto'o's second goal came courtesy of an excellent move involving Willian, whose performance will have put pressure on Eden Hazard, mysteriously dropped despite training with the side earlier in the week.
Jose Mourinho's reaction after the game: "I won't lie... Willian played very well."
Hulk helps out old teammates
Hulk has not always enjoyed his time at Zenit St Petersburg since joining from FC Porto 15 months ago, and Wednesday provided another of those dreary nights for the Brazilian forward.
Porto went ahead in the early kick-off in Russia, but Hulk leveled up following a defensive mix-up before facing his former teammate Helton after a penalty was awarded. Hulk possesses one of the most powerful shots in the modern game but still he elected to place the ball, and Helton saved it.
The game finished 1-1 and instead of being four points clear of Porto, Zenit is just one point ahead. But next up it faces Atletico Madrid, a 4-0 winner over Austria Vienna, and along with Bayern Munich, the only team with a perfect record after four games. Atletico is through; but Hulk cost Zenit dear.