You all should remember the time Itachi vs Kakashi, their sharingan level is totally difference. At Konoha, Kakashi just have normal sharingan with just one eye but Itachi already obtain Mangekyou Sharingan which can overcome sharingan user like kakashi.

For the second meet during Saving Gaara ARc, Itachi did not really in the fight because he just transform another person to fight Kakashi.