If your most senior employees are your worst employees then you have much deeper problems than the need to downsize.

The best people leave when conditions deteriorate not simply because you have a smaller workforce. Shuffle people between projects and scale back workloads as you scale back the workforce and nothing seems wrong.

It’s true not all jobs are findable so you’re going to need some onboarding and to let a some people go but that’s just a normal part of business.