As a fan of both fighters, I would love to see this fight.
Having said that, I think Anderson would either a) finish him via TKO or b) embarrass him for 5 rounds.
Stylistically , I think Diaz is tailor made for Ando. He's flat footed and comes forward constantly. Anderson is an awesome counter striker and will capitalize on that. Plus, Diaz won't have the size/reach advantage and isn't near as quick as Anderson. On top of that, Diaz doesn't work angles, although he does mix it up really well in the inside.
That would be a problem though. I don't see Diaz being able to get inside and do significant work. He has a good ability to fluster his opponent with his "punches in bunches" but none of those guys were counter strikers, or atleast o the level of, Anderson.
Lastly, Diaz fights with emotion, which can be good and bad, but he doesn't change his strategy on the fly. You know what to expect but it still flusters many of his opponents. It won't work with Anderson.
I will enjoy watching if it happens but at the same time, I'd be disappointed in Ando for taking this fight instead of a LHW. He doesn't have a lot of fights left and he'd consider fighting an established WW ? I just don't see Diaz coming close to giving Anderson problems, let alone winning.
And no, I never wanted to see him fight GSP.