LONDON -- Too often, the Champions League group stage is a procession, a dull stroll for the top-seeded teams into the knockout stage. But sometimes it produces groups like this one, with three excellent sides, all of whom are capable of beating each other on the day, all of whom would be worthy of a place in the last 16. When that happens, the margins are impossibly fine, the swings of emotion extreme.
In Arsenal's prior Champions League game, it was superb, producing arguably its best European performance since it reached the final in 2006 to see off Napoli. Yet now, having played both of its main rivals to progress at home -- and losing 2-1 to Borussia Dortmund at the Emirates on Tuesday -- it faces the very real prospect of elimination and will almost certainly have to win in either Dortmund or Naples to progress.
Arsenal didn't play badly against Dortmund and might even have won the game, but it was undone by a smart volley eight minutes from time from Robert Lewandowski.
The tendency at such moments is to analyze the move that led to the goal in detail, to ask whether the tireless Kevin Grosskreutz, a player not noted for his technical ability, really aimed his cross at Lewandowski or whether it was overhit; to ask why on earth Bacary Sagna was trailing behind the forward; and to admire the calm of Lewandowski who, after his profligate display for Poland in a World Cup qualifier last week, must have wondered if he would ever score in London on a Tuesday. There's a legitimate question too as to whether Lewandowski should have still been on the field, having perhaps been fortunate to receive only a yellow card after catching Laurent Koscielny with his elbow -- although there was no evidence of any real intent.
In a sense the bigger issue, though, is a more general one.
"It was a game of high intensity but very few chances," Arsenal manager Arsene Wenger said. "Dortmund were organized to stop us playing, and we were not as good as we can be. We put ourselves on the back foot with the first (Dortmund) goal. If you look at the number of saves our keeper had to make tonight and you concede two goals, we can only look at ourselves for not being mature enough. We cannot lose games like that.
"We started a bit hesitantly -- which we did not do against Napoli -- and we gave them confidence," Wenger continued. "Overall I believe that our fluent football going forward was not quick enough tonight. It can happen if you play many games. Some players physically are jaded at the moment."
There are two issues there. The one of naivety is perhaps a concern, although this is not that young a side and collectively it has plenty of Champions League experience. More significant in terms of this season, though, is the suggestion that Arsenal is jaded already. It has been unfortunate with injuries, losing Alex Oxlade-Chamberlain, Mathieu Flamini and Theo Walcott (and poor Abou Diaby, yet again), with Santi Cazorla just coming back. Jack Wilshere, meanwhile, is among the walking wounded, forced off yet again Tuesday with another recurrence of his ankle injury.
But that is not an unprecedented run of ill-fortune. Teams expect to carry two or three injuries at any one time and, in a sense, Wenger has been fortunate that Olivier Giroud, the only out and out center forward in the squad apart from Nicklas Bendtner, has remained fit. Lose him and there could be real problems. Even with him fit, if Arsenal is feeling so weary by October, it raises serious doubts about its ability to sustain a title challenge.
That aside and accepting that in a tight group Arsenal will almost certainly have to get a win in either Naples or Dortmund, there were plenty of positives for Arsenal. Although it had to overcome a flurry of Dortmund pressure at the beginning of each half -- Aaron Ramsey succumbing in the first to gift Dortmund an opening goal as he was caught in possession by Marco Reus, setting up a Henrik Mkhitaryan finish -- it came back to have the better of the end of both halves, even if it did end up being caught on the break. Olivier Giroud's goal in the 41st minutes came soon after Tomas Rosicky had forced Mats Hummels to clear off the line, such was Arsenal's control of the final minutes of the first half.
In a sense Arsenal took on Dortmund at its own game, completing 423 passes to Dortmund's 346. What probably proved decisive, as it has for Arsenal against Barcelona in recent seasons, was that Dortmund was rather better off the ball, running as a team over 11km farther than Arsenal in the game -- a sign of the intensity of its pressing. Wenger admitted that "physically" Dortmund was "a step above" any other team Arsenal has faced this season.
"The group is tight and difficult for us but possible," said Wenger, remaining optimistic. "We need a result away from home, but we can do that."
This, though, perhaps was a useful reminder that, as well as things are going for Arsenal, the squad is perhaps still a couple of players light.