Either Douglas jabs him silly at range or Douglas gets slept by a left hook. It's truly that simple in my book. A 50/50 fight that is decided by who wins the distance game. Inside Tua and outside Douglas.
Tua couldn't deal with a good jab Rahman jabbed him silly in both of their fights. With Tua needing to hit Rahman after the bell and also needing a dubious stoppage in their 1st meeting after being a mile behind on points. A focused Douglas who went 11-1 during 1986 to 1990 with wins over Page, Berick, M.Williams, McCall, Tyson. Would keep Tua on the end of his jab with that 83 inch reach and win a wide points victory. Tua could land a bomb out of nowhere after being behind on points and possibly score a late stoppage. But I'd favour Douglas on points he's a good skilled big man with an extremely long reach and he has a upper echelon jab to control Tua at range. That's not a good match up for the short plodding T-Rex armed Tua.
If it's Douglass on the night he beat Mike, Douglass easily, but any other time I feel like Tua would probably pull it off