There is a world of difference between, “I’m not sure about him. He’s doing a bad job.” and, “That was an error. I’m sure you can fix it and avoid it in the future.” Same goes for, “She’s an ace.” versus, “I am delighted at how you synthesized everything for the client.”
Managers must evaluate. They struggle when they focus on the merits of the individual. Great managers focus on behavior. And speak about the behavior specifically, directly, immediately, and often.
In your corner,
PS: Note I didn’t say anything about “bad managers.”
PPS: You can so do this.