Board Thread:Naruto Discussions/@comment-26636534-20180325094649/@comment-5085906-20180412165350

@Thrkillman I felt it was just too specific to be interpreted any other way. Shikaku pondered the possibility of a mind control jutsu and his first thought was not 'Shisui!' or any other renowned shinobi of his time which had strong genjutsu - no, he immediately thought of Itachi.

Though I guess you could argue he was more familliar with Itachi than he was woth Shisui, so I guess what you said makes sense too.