This is pretty tough man. But here's what I'll say. I don't know how Anakin will deal with Diavolo's speed. I'm one of those who are of the mind to say that Diavolo CAN attack in Time Erase due to previous feats of him doing exactly that. I do not see Anakin having a way to counter that ability. And if Diavolo see the future and sees that he has killed Anakin, then Anakin will be dead, as we know that, at this point, Anakin does not have the ability to deny fate, as the entirety of Revenge of the Sith was about him trying to deny fate and failing, causing his fall to the Dark Side.
Now things are different should Diavolo not be allowed to doughnut in Time Erase. If Diavolo in this battle is assume to NOT BE ABLE to attack in Time Erase, then the chances of victory shift to Anakin, as Anakin himself has his own form of precognition through the force, which allows him to sense where things will be before they even get there. It's how Jedi deflect blaster bolts with their lightsabers, and how Anakin won the podrace. Jedi reaction speed is beyond instant as they can react to things that have yet to happen, and this gives Anakin an edge. Now, he might not have the same level of accuracy in knowing what will happen as Diavolo does (As I'm pretty sure Anakin's dreams were said to have come from Palpatine), but he does get somewhat autonomous movement in a way not too unlike Ultra Instinct due to the force somewhat controlling his body if he lets it.
It becomes a toss up depending on what you feel the extent of their powers are.
Diavalo 
Anakin Skywalker (Part III only)
