Query: What do international leagues' friendlies happen in the middle of?
Context: This is essential, since national squads generally have much less time together in which to prepare. The biggest difference between friendlies at the club and international levels is that international friendlies mostly take place during club league seasons, not between them. This has on occasion led to disagreement between national associations and clubs as to the availability of players, who could become injured or fatigued in a friendly.