How are you not understanding this?
Play 1 game per week = less chance of injury.
Play 1 PL game + 2 internationals = more chance of injury.
You living in a world were players only get injured during matches?
Players that doesn't play matches, train more, train harder, train with higher intensity and are much likely to get injured during training.
Branthwaite didn't get injured during match and has had setbacks in training. Garner was injured in training. Same with Tarkowski and Keane.
We also see again and again that players that have had long term injuries often pick up other injuries when they start playing matches. Because their body is not used to the impact of playing games. While players that are used to play twice a week, seems to be able to that 11 months a year without picking up more injuries than players that hardly play matches.
I expect Dyche to do a mini preseason during the international break. To get new players up to speed. For those players that was injured during the summer. They will train hard. They are likely to play at least one match behind closed doors. We should expect injuries among those spending the break at Finch Farm. It is a part of football. If you don't get injured players, you're doing it wrong.
I don't expect Coleman to get back to Premier League standard and struggle to see him getting minutes for any other team in the league, but to get there, he needs to play matches. It has been to much training and too few matches the last seasons. To get through a couple of low quality and moderately paced international matches can be exactly what he needs.