How important is a settled back four?

Rotation keeps players fresh, but understanding between defenders takes time.

Is a settled defence worth sacrificing freshness, or is rotation overrated?

Freshness is nice, but defensive chemistry is earned in the trenches. Constant changes in the back four always show up in those frantic final ten minutes when communication breaks down and markers get lost. When center-backs don't know each other's blind spots, that is usually when teams concede those cheap late winners. You can rotate your wingers all day without hurting the structure too much, but the spine needs consistency. Does anyone think a manager is better off risking a makeshift partnership just to rest a guy?