Several centers still available in the portal.

CorpusJayhawk wrote: All rankings from ESPN. Cisse is raw offensively but sure would be an asset in the defensive side and doesn’t strike me as a starter type player. He might be willing to come back-up Dickinson. Don’t know anything about Bandaogo or Nelson. Collins was once a 5 star HS recruit.

14. Aziz Bandaogo, 7-0, C, Soph., Utah Valley Wolverines
15. Grant Nelson, 6-11, PF, Jr., North Dakota State Bison
28. Moussa Cisse, 7-1, C, Jr., Oklahoma State Cowboys
92. Daimion Collins, 6-9, PF, Soph., Kentucky Wildcats

Bandaogo would be a 2x transfer, and with the new rules in effect for next season athletes are unlikely to be okayed to play next fall (have to sit out).

Nelson is in the NBA Draft and invited to the combine. He is also in the portal, but most agree he will not be looking to be a backup should he opt to return & transfer.

No info on Cisse or Collins.

Thinking along lines of “who would be willing to come to be a backup”, Christian’s 6-10 brother Parker Braun is a graduate transfer (no sitting out) from Santa Clara being discussed by some. Not a great choice, but if you’re talking about 5-10 minutes and 5 fouls backing up Dickinson (or KJ at 5 should Self go small) he might end up an option.??

More on Bandaogo -- he might get waiver to transfer again, but Cal may be the favorite.
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On Cisse, he started his career at Memphis, and has two years of eligibility left, but because of the new 2x transfer rule will need to ask for a waiver same as Bandaogo. Unlike Bandaogo, it is not known on what grounds he would request such a waiver.
Still, if he has to sit, it might be worth the ride for Self to offer him, have him sit a year behind Dickinson and then potentially beat him out for the starting role in year 2 at KU. He has already been Big 12 DPOY, so he would potentially be an upgrade from Udeh but for not being able to play next season.
Link

Daimion Collins has played more a a forward at UK, and at 6-9/210 would be on the small side for a C, but he might make up the difference with other skills/talents/attributes. Just don't know. 247Sports Transfer Portal has him listed as a C, so there's that.