Originally posted by: raijin
Actually, the manga has mentioned it, but the current circulating translated chapter where it is said is somewhat mistranslated.
Although I could do a translation myself from the raw manga, here is the conversation (from the manga) between Itachi and Kisame after their confrontation with the Konoha Jounins translated by AK of Troy (the individual who translated Naruto Volumes 1-12 and is the translator at Toriyama's World):
Kisame - You may be able to keep up with him but I don't know about me...
Kisame - He's on a different level
Itachi - Yeah... Fight him and we either both end up dead or get lucky and get a draw
Itachi - Increasing our numbers likely won't make a difference
Kisame - We finally find him at the ramen place and his bodyguard is one of those "legendary three nins"...
Kisame - Against him, the name of the "Leaf's Uchiha Clan" and the "Mist Seven Shinobi Swordsman" will just be tarnished...
Itachi - Yeah... But...
Itachi - Even the most powerful have a weakness...