This could've happened in the early 80's when Wilfred had the WBC super-welter (junior-middle) crown.
I was a great admirer of Benitez's slick boxing style and how he slipped punches with ease. He had the same problem with Tommy Hearns that others did (His size)
Hagler of course pounded Hearns pillar to post, but I 'll never understand why Tommy didn't use his very underrated boxing skills, which would have made it a much less action packed, but more tactically interesting (and closer) fight.
I believe that in a 12-rounder Wilfred could've beaten Hagler by decision, but probably not in a 15-rounder.
Hagler seemed to be more effective when he was boxing and setting up counters than when he had to lead in a fight. Against a slick fighter like Benitez he might have been in for a frustrating evening, though he might have worn him down in a 15 round fight (late round KO possibly).