Board Thread:Naruto Discussions/@comment-12509038-20140806073433/@comment-3568954-20140807050838

AsianReaper wrote: Itachi had horrible chakra levels too, but he had the sharingan activated almost all the time, only deactivating it when using the mangekyo. His chakra level was lower than Kakashi's. It's listed at 2.5, while Kakashi has 3 (cited from Itachi's page). While it did drain a lot because he didn't deactivate it, the sharingan drained Kakashi mostly because he couldn't actually awaken it like an Uchiha. His body couldn't handle the eye like a normal Uchiha could.

exactly and look at it this way, Obito did not awaken the Rinnegan so when he used the single one. it was overwhelming since kakashi awakened these eyes he likely will have no drain like before