Now, before I proceed to dissect the most gaping chink in Sonnen's armor, I think it's important to give him props for doing alot better than many thought he would.  I doubt anyone expected Chael to hurt Anderson with standing strikes, and he was doing very well until... well, you know.

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 So here's the real question- we all know that Chael's tragic downfall throughout his career has been his submission defense; but is that really from a lack of awareness & knowledge of submissions/ lack of natural aptitude or savvy for submission grappling?  Or is it something mental?  Here's an anecdotal story of mine that you'll have to take at face value (explained here in a comment I posted in another thread a while back), which makes me lean towards the latter of the two:

 I once sat on a plane several years back next to a pro MMA fighter who split his time between Xtreme Couture in Vegas and Team Quest in portland. 6’2, 255 of solid muscle, the dude was a brick shithouse.  The fighter was Josh Bennett,  one of Chael’s main training partners up at TQ.

We started talking about the Sonnen/ Filho fight (their 1’st fight in the WEC); obviously Chael was laying quite the beating on him- outstriking him from range, beating him up on the ground, and fighting off armbar/ triangle attempts. Now, Chael’s achilles heel has always been his submission defense- Prangley, Forrest, Horn (2x), Babalu, and Maia all submitted him. Marquardt almost slept him with a guillotine. Against Filho, Chael got armbarred from within his guard.

Bennett said that in a fight, in the subconscious of every man is the "fight or flight" instinct coming into play; the exhausting, unbearable pain that MMAists endure during a fight is constantly pushing on the natural "flight" instinct, and so some guys will instinctively look for ways out. He said that not only have he and Chael’s trainer’s noticed this, but that Sonnen himself has mentioned it, but he said that many times Chael will give up submissions easier than he should, as a way out. At that level, everyone’s technique and ability are so elite, if you don’t have 100% resolve at all times, you will get caught with your pants down.

Chael has seemingly showed improvement in this area, surviving sub attempts by Okami, Dan Miller, and Marquardt, but Anderson has such a steel resolve, and such dramatic finishing abilities, I tend to think that at some point during that grueling 25 minutes, Chael will give an inch. Anderson will take a mile.

That’s just my $.02

 Not to say I told you so or anything, especially since my post 3 weeks prior to the bout (Silva vs. Sonnen: an in depth analysis) outlined the same narrative that most analysts honed in on regarding the fight, that Andy's offensive dynamism would be the deciding factor in the fight, and that Silva would (at some point in the 25 minutes of action) catch Sonnen with devastating strikes or a submission.  While the expected outcome did happen, Anderson was dominated up until then much more thoroughly, and the fight lasted longer than most had expected.

Now, i'm not trying to fighter bash or anything here; I have a ton of respect for Chael and his abilities.  But I just think that with as much experience he has, and with how many times he's been submitted (by triangles, especially), I think it's more than just a problem with his ground skills.  The way he stubbornly wades in competent grapplers guards, and sometimes becomes reckless with his ground and pound is his way out; he rids himself of the strains of intense focus & concentration on technique/ strategy.  The submission is a respite from the grueling toll a fight takes on your body, and that seems to be more a part of Chael's psyche & character than a lack of mat savvy.

I don't know if Sonnen should seek a sports psychologist (although it surely couldn't hurt, and has seemed to help guys like GSP), but I do know that there is something keeping him from the top, and that something will determine whether he can reach the pinnacle of the sport.  Because he showed that he has the physical tools & skillset to beat Anderson Silva, but not the will.