Although Donaire may be old, he is still worth watching as long as he keeps winning.
That's being conditional, I think we cannot guarantee that he will win. When he fought Inoue, he was still entertaining to watch because he wasn't afraid to go toe-to-toe, and I liked his confidence in believing he could beat Inoue via knockout, which is why he let his guards off. However, Inoue is an exceptional fighter, and it won't be the same with Santiago, as he's not on the same level as Inoue.
That's true, but if I were Nonito Donaire, I won't let my guard down against Santiago too. Donaire already felt the defeat against Inoue and it must've affected him bigtime mentally, but I believe he will probably come back stronger and he should still stay aggressive with his moves as that is what he is known for.
By not letting Santiago have control of the pace of the game, he will probably win this without heavy damage. That way, whatever he is pursuing next, if it's unifying the titles, then he can do it in a sudden schedule.
He is getting old, he must make haste if he truly wants to achieve what Inoue did.
That sounded like I already concluded the winner but I know he will be.