Who taught DADA before Quirrell?

[Ersatz Harry]

No: HPFGUIDX 138141

Perhaps this has been dealt with way back in the archives somewhere,
but I found myself wondering about this today and went back to SS/PS
to see if Quirrell's predecessor was mentioned.  No such professor was
named as far as I could find in a quick pass through the book.

In fact, there were a couple of things that made me think that
Quirrell had in fact been the DADA professor the year before Harry
starts.  For one, Harry meets Quirrell before school actually starts
(on the way to Diagon Alley with Hagrid to pick up his school things),
and Quirrell says nothing about teaching DADA for the first time, only
that he teaches it.  For two, Dumbledore makes no mention of new
professors at the welcoming feast that year (as he does in some of the
other books).

So I see multiple possibilities here:

(1) I simply missed something (this is probably the most likely);

(2) JKR goofed a little bit in the writing of SS/PS; or

(3) JKR did not really settle on the one DADA professor per year idea
until *after* writing SS/PS.

Am I missing any possibilities?  Anyone have thoughts on the three above?

Ersatz Harry