Two weeks ago, Arsenal was still in the running for a hypothetical Grand Slam of titles. It was in the final of the League Cup. It was one game removed from the quarterfinal of the FA Cup. It had beaten mighty Barcelona in the first leg of the Champions League Round of 16. And in the Premier League, it was in second place, four points behind Manchester United, with a head-to-head clash coming up at home on April Fools' Day.

Over the past few years, despite playing some of the best European soccer this side of Barcelona, Arsenal...