The thing about international breaks is that it makes the schedule for the clubs very brutal. This is the case for Barcelona in the month of September.
Starting on Saturday against Alavés, the Catalan giants have six matches in 18 days, a brutal schedule that will truly test the Blaugrana squad, that was built this season to work through busy periods like this one.
The interesting and coincidental (or not) thing about September's calendar is that Barça have two games at home to start and two games on the road to finish the month. The first two matches are relatively easy, against Alavés in La Liga and then against Celtic in the Champions League opener. These are very winnable games even with rotated teams mixing starters and reserves, so they shouldn't be that big of a problem.
After a road trip to face Leganés, which also doesn't look that tough, three very difficult matches in nine days: first there's Atlético Madrid at home, and we know those aren't fun. Up next, Sporting Gijón away, which wasn't an easy fixture last season and is just three days before a Champions League trip to Borussia Mönchengladbach that promises to be one of toughest games in the first half of the season.
Lucho won a Treble in his first season rotating the team in these kinds of situations. He's now got the squad to do it again this season, and if September goes well, then the rotation formula will still work and can be used for October and November, that also have international breaks and crazy calendars.