Unlike in the above referenced example of more subtle and less frequent guitar growl, this one is more obvious and pretty consistent throughout much of the song. None the less, once I heard it I thought it was pretty cool. It doesn’t exist in the studio version that I have noticed, but it is definitely present in the live version from the Eric Clapton album Just One Night. I believe it’s coming from the rhythm guitar but it definitely isn’t coming from Clapton’s guitar because it is still audible (and growling with the rhythm) while he is playing solos.
Give a listen from 0:18-0:22 and 0:26-0:30 for examples, but again, the growl is there in much of the song, and particularly noticeable in the first half.