Conceivably they come to camp with 8-10 guys vying for a spot in the rotation. That's not saying 8-10 strong candidates. just that the situation is unsettled enough, and they have enough guys who are fighting for spots that it could be that many.
Arietta
Hendricks
Wada
Wood
Jackson
Straily
Dubrount
Turner
Beeler
That doesn't count Rusin, Grimm, Ramirez - all of whom I think will stay in the pen.
It doesn't count Vizcaino - not sure if he'll go back to starting or where he'll be.
It doesn't count Pierce Johnson, who may be a little ways off, but not sure.
It also does not count any FA signings, and I will be very surprised if they don't sign at least one pitcher. Though if they do go get a TOR type, the 5 may be settled with the guys on the top of that list.
But it could be a crowded battle for the last spot.