He didnt need Mangekyou to beat Kurenai since she is a rookie jounin anyways [img]i/expressions/face-icon-small-smile.gif[/img]

And Mangekyou drains to much stamina/chakra and its Itachi's best offence, so he saves it for strong opponents, cuz how often can he use it? 2/3 times a day or something...