it was in an article about friendlies:
"The solution we’ll be implementing will be two-fold. First off, Competition matches will need to be at least 3 hours apart. That means that if you, for example, have a League match, your next Cup or Champions League match will be at least 3 hours after it, giving you enough time to recover and prepare. This restriction also applies to Friendlies, meaning your friends won’t be able to schedule a Friendly match if your next Competition match is within the next 3 hours."