The people I trust near the program say it is his back, and as impactful of a player as he has been for us, given his injury history he may be made of glass.
2020 - Didn't finish the season due to injury (though, he should get a pass for this since KU was basically playing with a bad FCS offensive line).
2021 - Plan was to redshirt him since KU was again playing with a bad FCS offensive line. But Jason Bean and Miles Kendrick both got hurt so they had to play Daniels against KSU. He was such an obvious improvement that Daniels, his parents, and Leipold got on a conference call and decided, go for it - play out the rest of the season (with the major result being the win over Texas).
2022 - Injured vs. TCU and didn't play the rest of the regular season. Returned for the bowl game.
2023 - Back injury in pre-season. Missed the opener, played three straight, now has missed four straight.