If anything, I think health/age may tamale a toll. Both have similiar offensive capabilities, with junior having more tools and ngannou having the better reach. Both have KO power, sharp boxing, command of angles, and this fight determines a lot for both. I have a feeling both will b a bit more careful in the first than usual.
I could see JDS being real defensive, playing the boxing game and potshotting and moving the first round, and taking the lead. I have a feeling he will have to move a fuckton to deal with ngannous reach, and considering what happens his last fight, I think he will b a little skittish to kick the legs. My bet, is after evading and outstriking ngannou for a bit, he starts showing down and gets slept.
Or ngannou gets too excited, swings wide, and gets caught. But his boxing is looking sharper and tighter. Not seeing a lot of ways he loses in this.
If JDS really wants to win, I'd honestly tell the guy to strictly wrestle fuck ngannou after round 1, and run like a bitch after round 3. Seeing as JDS is a fucking warrior, I'm betting he will end on his shield as such.