McGregor won the 2016 UFC lightweight title and held off Eddie Alvarez at UFC 205.
Stevenson, a former featherweight champion, was nothing short of sublime in the first half of his 130-pound bout against Jamel Herring.
Ryan Garcia will undergo a surgery for the injury on Monday and is expected to be sidelined into 2022, postponing the bout with Diaz.
A razor-tight decision, which saw Taylor triumph (96-94, 96-95, 96-95) on the cards, deserved a raucous crowd in Manchester.