Giardello would win a decision, over either 12 or 15 rounds. Giardello at his best, that is...and I believe that's what these type matches are predicated upon..both guys at heir best, that is. Joey would be too wily, tough and clever for Duran.
Two boxing IQs that were off the charts. At middleweight an in shape Duran still had some hand speed. But (as Cobra said) an in shape Giardello would be able to step around Duran and pick him off as he came forward. This goes the distance, and it would be interesting watching this chess match, Duran will time some right hands on Joey, but Giardello would find out that Duran could not pull off as many cute tricks if he were forced to lead, and Duran could not impose himself physically on Giardello. Giardello by clear decision.
Giardello, he's certainly durable enough, and that really eliminates a lot of Duran's chances imo. Giardello isn't the greatest combination puncher in middleweight history, and I think Duran would be able to get shots off a good deal in exchanges, which would happen seen as Giardello isn't the type to get 'on his bike'. But Giardello's footwork is immense, and he is the stronger man here, he'd impose his left hand on Duran and take the decision I'd say. Some of the countering and feinting going on would be great in this.