ΔE 66.8, poor: a clearly different colour, so not a substitute. Chipping Medium is noticeably lighter, much more muted than Nurgle's Rot.
Not as a straight swap; see the closer alternatives below. Poor match (ΔE 67). Chipping Medium is noticeably lighter, much more muted than Nurgle's Rot.
The same difference applies the other way round: Nurgle's Rot is noticeably darker, much more saturated.
ΔE is the colour difference between our two swatch estimates: under 2 is a perfect match (you’d struggle to tell them apart), under 6 very close, under 10 close, under 15 fair, under 20 loose, under 30 very loose, and 30 or more a poor match. Real paints also differ in finish, coverage and how they thin, so test before you commit.
See Nurgle's Rot on the colour wheel See Chipping Medium on the colour wheel
All matches: Nurgle's Rot equivalents · Chipping Medium equivalents