1 Work in Hyuuga Hinata & Uchiha Shisui
The day that Danzou tore Shisui's eye right out of his head was the day that he came so close to killing himself the psychs were tempted to label it as a suicide attempt. (It was also the day that Shisui stopped a civil war and incidentally exposed Danzou for all his wrongdoings but that by no means outweighs the fact that shisui almost killed himself)
So when he ends up Team 8's Jounin Sensei he's less than convinced he's the person for the job.
Read: Shisui is more than capable to be a Jounin sensei and apparently everyone can see that but him.