Speech therapist here. I’m not sure what you mean by the question. Typically for someone with an articulation disorder an r will be replaced with a vowel. Ex wabbit for rabbit, bud for bird etc. Many different accents also drop the r in middle and ends of words. As far as “d” it is often substituted for the “th” sound, and rarely for a k or g sound. I’ve beer heard of a d for r substitution. Are you beginning to do that in your speech to avoid stuttering?