As I see it, KU has two big unknowns coming into the season. Coach Self may already know the answer but we certainly don't. The unknowns are PG and Center.
Let me start by saying that in my opinion the SG and SF, and to an extent PF, are pretty much set with Selden and Oubre starting, Frankamp backing up the SG and Green the SF and Svi likley playing both positions and at time Ellis stepping back and plain SF when Coach Self goes big. I don't see any other players involved in these two positions although Graham might. The PF also seems pretty well stocked with Ellis and Alexander getting the lion's share of minute and Traylor backing them up.
Note: The official KU roster lists Ellis at 6'-8" -225, Alexander at 6'-8" - 240, Traylor at 6'-8" - 220, Lucas at 6'_10" - 240 and Michelson at 6'-10" - 245. They are all listed as "forwards."
The two unknowns I see are:
Unknown 1, Point Guard - We have discussed extensively who will start the season but we still don't have an definite answer.
Unknown 2, Center - Who will start a center?
My answer 1 - Mason has the inside track and can play a faster tempo. Frankamp is the steadier player but tempo would be slower when he is at the helm, on the other hand he can also play SG by virtue of his potential 3 point shooting potential. The biggest unknown is Graham that supposedly is the ultimate combo guard; I don't know much about him so I am not sure where he will play in the rotation. If I were a betting man I would go with Mason at the PG to start the season.
My answer 2 - Alexander would seem the likely starter but being only a "KU" 6'-8 would certainly place him at a disadvantage against the taller centers in the league and his heft might tire him quicker until Hudy has worked her miracles, so we might get only limited playing time at the start, and let's not forget about the "freshman wall" that comes later in the season. Mickelson would appear to be the better suited to play center and his playing time will depend heavily in his off-season development. If he has indeed increased his jump by 6" then he might be in line to be the next pure rim defender that Coach Self likes and has enjoyed in recent years with Aldrich and Withey. Lucas falls somewhere in between the other two. My answer, Alexander start at Center and Mickelson gets substantial minutes.
Bonus Question - Which unknown is a bigger concern?
My answer - No doubt the PG situation. The road to the Championship starts with an elite PG. Just about every team that has won the National title had an elite PG to lead the team. PG play (and Embiid injury at tournament time) was the Achilles heel of last year's team. Superior PG play, (absent a super start at other position) will get you farther than just about any other position.