Like i said in an early post itachi can use a genjutsu on the 4th just like the one sasuke use on danzo and make the 4th think he is at top speed when he is only walking and BOOM a hard slap with sansono and then light him up with the black flames,and he is all done (The genjutsu is not painful or changes any back ground so no chakara will be disdurb.On top of that itachi is the master of genjutsu so he can pull it much perfect than the way sasuke did.