The Simpsons have, over their quarter-century existance, done episodes dedicated to every sport. From baseball (the legendary 'Homer at the Bat' and the underrated late-season 'MoneyBart') to football (there's an episode dedicated to it, but let's all just remember Joe Namath's haircut inspiring Homer's mom to become an anarchist) to hockey. There's even a single 2007 episode of the show with (forgettable, vocally) guest star Ronaldo that deals with soccer. Unless you count the episode above.
However, The Simpsons are going back to the soccer well, as well as back to another main plot point of that episode in a March 2014 show "inspired by" the World Cup, according to a Fox press release. Homer becomes a soccer referee (happened in that Ronaldo episode, titlted 'Marge Gamer') whose work eventually leads him to Brazil (which also happened in a previous episode, where the family goes to Brazil in 'Blame it On Lisa').
The main plot point is that Homer's referee career forces him to deal with South American gangsters that try and get him involved with match fixing. You have to love how some sports leagues are allowed to be portrayed on television. The NFL said no to stuff like Playmakers and a plotline on The Good Wife that could have made them look bad. FIFA, however, goes "you betcha Homer's confronted with match fixing!"
Anyway, the episode is part of a Fox branding campaign that will see the show partnering with teams across the world, including FC Barcelona, to provide Simpsons-themed merchandise. Just make sure everyone gets a fair percentage of t-shirt sales. That's the sweetest plum!