I see Napoles out slicking Cuevas, countering him as he misses his big bombs. Mantequilla would drag Pipino into a place that he is unfamiliar with, going into the later rounds. Napoles knowing that Cuevas has dynamite in his dukes, does not give him the opportunity to connect, Jose Mantequilla Napoles by unanimous decision.
One is among the most underrated greats at welter (by the unwashed multitudes that is; most respectable journalists and historians place him top 5 or near enough) and the other perhaps the division's most overrated belt holder IMO.
Cuevas was tailor made for Napoles. Though Cuevas may have the single most devastating punch in welter history in his left hook., his other skills were good, but nothing to write home about. Napoles was the complete package. Napoles could stop Cuevas if the fight goes beyond 10 rds. But more than likely he would cruise to a wide decision win.