Mainz 05 3-1 Borussia Dortmund
Can's tackle on Lee Jae-Sung was indeed unnecessary. He couldn't have won that ball from the Mainz player due to the distance between them and the best he could have done was to tightly mark him or prepare to intercept. A two-footed challenge with studs showing was always going to lead to a red card.
Borussia Dortmund, even with 11 men, were struggling to take control of the game as Mainz were easily able to find spaces to exploit in those early stages. While Dortmund couldn't make the most of their dominance in possession. In such situations, knowing that your away form is not good and injuries have stretched the squad thin, a captain should have focused on controlling the tempo of the game by restoring some calmness. But unfortunately, Can erred in his decision making.
The red card turned out to be the game-changer as it ended any hopes of Borussia Dortmund getting the three points and Mainz eventually clinched a well deserved and convincing win.