I'm not going to say that Bosz should be a candidate for a big club at the moment, but I wouldn't damn him for his time at Dortmund either.
- The season started with Dembele forcing a move, after the pre-season, with him as the creative head of the team, was done.
- Auba started acting up, apparently showing increasing disciplinary problems, putting Bosz in the dilemma that he either had to suspend one of his best strikers without backup or cause division by tolerating his behaviour
- Weigl, Dortmund's supposed midfield head, came back from an injury a couple of weeks after the season started, made critical mistakes and either was unable or refused to (probably both) to function in Bosz's role
- Jeremy Toljan, Dortmund's new fullback that season, was absolutely disastrous in defense, literal school boy defending, but since the squad was a bit thin on that position and both Schmelzer and Piszczek picked up week-long injuries Bosz still had to play him almost every game.
- Reus not being able to play a single minute for him
- Bartra, not that I would ever blame him for it, losing it completely in the middle of Bosz's tenure.
- To some degree bad luck: especially in the game against Schalke, when Auba missed a sitter at 4:0 and then got himself sent off - a win there would've shifted momentum a lot.
- The club and players not having come to terms with the bus attack at the time, especially since the trial was beginning in winter.
Obviously we can criticize that Bosz should've realized that he didn't have enough fight in his midfield, his CBs were unable to cope with his high line and he should have reacted quicker and been more pragmatic until the squad was right for his style. But it's also true that Stöger couldn't perform satisfactory with the squad either (despite getting rid of Aubameyang, getting Akanji and having Reus fit).
Dortmund did a huge overhaul this summer for a reason, they introduced Kehl as a squad manager, to have a closer eye on squad dynamics and problems, they hired Sammer as an external adviser, they got rid of Sokratis and together with signing Akanji and Diallo completely replaced the CBs Bosz had to work with. Toljan, who Bosz had to field every game, was phased out under Stöger and now that Hakimi was signed he didn't play a single minute under Favre. They added combativeness and a lot of leadership mentality to their midfield in Witsel and Delaney. Weigl has been relegated to a bench role, Sahin has been sold. So has Yarmolenko, who was the attacking marquee signing of Bosz's period.
