Thomas Tuchel has toppled the La Liga leaders. He has sent Chelsea surging up the table, inheriting a stumbling side and taking them on an unbeaten run. He has transformed their defensive record to such an extent that Antonio Rudiger has accidentally scored as many goals against his own team as all of their eight opponents have between them.
Suffice to say his reign has begun more auspiciously than Frank Lampard's, whose managerial bow was a 4-0 defeat by Manchester United. But as Tuchel, who first lost to and then beat United in the Champions League with Paris Saint-Germain, prepares to renew acquaintances with them, the toughest part of the task lies ahead of him.