Seb as intelligent, but almost purely tactical,

getting into Jim's head is something that would barely occur to him,

And that is why Seb will always be the lieutenant, never the commander. Part of being tactical is getting into your opponent's head -- "Rommel, you magnificent bastard, I read your book!" (http://www.youtube.com/watch?v=AJXKVOxqkWM) -- and if Seb doesn't even think to do that, no wonder he's wound up working for someone like Jim.