I only watched it again a few months ago and Nelson started very strongly and won the first three rounds but Fenech landed a huge right towards the end of that round that really slowed the Professor up.
From then on it was a war which IMO Fenech won and won well. It's true the commentators thought so too during the fight as Nelson appeared to be getting a beating and they were saying he should retire?
It is a true champion like Nelson who comesback and wins the rematch not many thought he would and then go on and fight for a few more years. A terrific fighter.