People think I'm a sociapath so take my advice as you will, but the way I would frame it is plain and simple: be honest, brief, and vulnerable. Something along

People think I'm a sociapath so take my advice as you will, but the way I would frame it is plain and simple: be honest, brief, and vulnerable. Something along the lines of "This is a hard thing to bring up, but I think you may be underperforming. Do you feel like this is the case? How can I help?"