Could take the other side a few different ways, but the one I'll saddle up for now is that Smyly almost certainly knew his arm was about to melt down, so he decided to make as big of a statement on the WBC stage as possible, so as to better market himself to other clubs.
Could also be, if that was the case, that such a decision would have left M's management cold to the idea of a return.
These guys walk around with aches and pains their entire adult lives--pains that would put us mortal men down and begging for heavy duty painkillers. They *know* when something's 'not right,' and the *know* when their golden ticket's about to go POOF because a crucial ligament's about to give out.
For these guys, their body is indeed their temple. Precious few of the veteran players are unaware of their own physiologies to the point that they aren't aware, overtly and consciously, that their <fill in your favorite crucial ligament/muscle here> is about to give out.