Bob Koester, of Delmark Records, remembers Junior Well
"I first heard Junior Wells on the States 78's of "Hoodoo Man", etc. during my days in St. Louis. I later heard the Muddy Waters band on a trip to Chicago, at the Club Zanzibar c.1957 and was perturbed that Little Walter had left and a new guy had taken his place but when I requested Key To The Highway and Muddy said, "I think Junior Wells does that better than I do," Junior certainly cut Walter in the vocal department."
And more fascinating insights from Bob Koester, at this interesting URL