Tactics
Niko Kovač's tactical approach is very vertical and tends to be focused more on a solid defensive structure, but he has proven to be flexible at needed times. For starters, his spell at Eintracht Frankfurt showed a vertical/transitional style but with patience while in possession, with a lot of incisive passes and players who fought for every ball.
His defensive shape tended to force the opposition to attack wide, as he liked to induce long balls by applying a high-press strategy in those channels to recover possession. In Frankfurt, he mostly played with a back-three and forward-oriented wingbacks, but he also varied his formations a lot. While in Münich, Kovač needed to adapt to Bayern's dominant traditions, opting for a back four most of the time.
However, Niko struggled to diverge from his original style, as Bayern was given the majority of possession in most games. He used to rotate the team frequently, which caused internal friction, with players and board members openly criticizing him. Despite his silverware-winning tenure in Münich, he underperformed in xG, xGA, and expected points compared to Jupp Heynckes, leading up to his sacking.
At AS Monaco, Kovač had more freedom to switch formations and impose his style, as he had a physically gifted squad in his hands, like Frankfurt. Although his style was kept the same, Kovač wanted his team to be well-proven in possession compared to his Frankfurt's 48% average with the ball. An overall underrated job at the principate, considering the circumstances and clear disadvantage to PSG's wealth.
Lastly, his Wolfsburg side used variations but primarily a back-four formation, mixing between a 4-3-3 and a 4-2-3-1. This pretty recent approach was reasonably similar to his Bayern's, and it could be used in BVB once the Black-and-Yellows have enough defensive depth to play three center-backs. With likely different variations and an unmistakable style, Kovač has enough tactical knowledge to try to fix this BVB.