If Hagler stays behind his jab, he wins all three. If he gets too confident, Tiger could well outbrawl him. Hagler would need one of his ultra disciplined performances, and as he won't hurt Tiger, it will need to stay that way throughout.
IMO Hagler does well stylistically against the more aggressive, come forward middleweights...I'd pick Hagler by decision in some good fights.
Hagler would have to follow the time honored prescription for beating Tiger,...jab and move...box, box, box...all night long.
If Hagler uses his skills he wins all three if he decides to go to war with Tiger things will get complicated for him and he loses at least once maybe twice to the great african fighter.
I was a massive Hagler fan growing up, but the first Antuofermo fight always troubled me. Hagler was unimpressive against a light hitting mauler and I can't understand why. This gives credence to people who think Zale or Tiger might be able to bully Hagler, too. Roldan was also giving Hagler all he could handle until he got the eye injury. I still rate Marvin for his overall accomplishments and all round ability and he did improve in the second Vito fight. He would probably outpoint Tiger but it wouldn't be a cakewalk for sure.
Tiger though past his best and weight drained for years making middleweight had an outstanding record against the cream of the division. He accomplished something Marvin never attempted ; lineal champion at a higher weight. A win apiece with a draw seems a reasonable outcome of a trilogy.