OK, I'm going to recommend something here that I've never tried before, so I can't guarantee that it will work. It involves making changes in the storyline database, so the first thing you'll need to do is make a back-up copy of that file in case something goes wrong.
You can find the storyline DB (default_storylines.xml) in the storylines folder. You can open it in Notepad++ or any other application that can read XML files. Go to storyline 232 (you can do a search for "football"). It should look something like this:
To decrease the frequency of the storyline, change the "random_frequency" value to something lower than 1000. To increase the interval between occurrences of this storyline, change the "min_usage_interval_days" value to something higher than 1000.
Once you've made your changes and saved them, you will need to reload the storyline database. To do that, go to the Game Settings screen and choose the Database tab. In the upper-right corner of that tab is a pull-down menu named Tools. Select that menu. Among the options is "Re-import storylines database from XML file."
As I said, I've never tried making changes directly in the storylines XML file. Let me know if it works.