The way I sort of look at the floor of TSJ if he plays minutes I see him being able to play reasonably serviceable minutes in the mold of Taurean Prince and Troy Brown Jr. What I mean is those guys mostly stay in their lane don't screw up and offer a few solid strengths.
Prince of that group is easily the best shooter and best scorer although TSJ has potential there. Brown Jr was easily a better defender than Prince and was able to actually guard forwards physically and was a much better enounder. TSJ seems more like a guy that might be able to guard 1-3 and maybe mature enough physically to put up some resistance if switched onto a typical NBA PF. It seems like he won't just be a compete disaster from 3 and can offer something in transition.
Prince may be a little better player than Brown but I'm not sure the difference is vast. If TSJ this season when called on can for the most part be solid defensively, not screw up on offense and therefore not be a big negative (he is a rookie so probably will be a slight negative) that's not bad. There is clearly more potential from him to be more but watching him it feels like he has a solid floor. He isn't a scorer that has to learn how to play defense or figure out how to fill a role. He did all those things for a number of games during his 5 years of college. Like a number of other players we have drafted in the last few years I feel pretty confident his defense is gonna translate.