No, selecting a token for Shire Shirriff doesn’t contain concentrating on and the flexibility cannot be fizzled by destroying that token. The token is chosen solely as soon as, when the flexibility resolves.
The token for Shire Shirriff’s potential just isn’t chosen as a goal as a result of it’s not preceded by the phrase “goal”.
115.1d A triggered potential is focused if it identifies one thing it’ll have an effect on through the use of the phrase “goal [something],” the place the “one thing” is a phrase that describes an object and/or participant. The goal(s) are chosen as the flexibility is placed on the stack; see rule 603.3d.
Which means the selection of token occurs solely at decision, and the participant doesn’t must announce the selection beforehand. Irrespective of which token you destroy earlier than the flexibility begins to resolve, so long as there may be one token remaining, the participant can select that one.
Hypothetically, if the selection of token was made by way of concentrating on, then the selection could be locked in when the flexibility triggers and you possibly can destroy that particular token. Nevertheless, the flexibility would nonetheless not fizzle as a result of it has one other goal: the creature to be exiled. So long as a focused spell or potential has a minimum of one legitimate goal remaining, it’ll resolve and do as a lot as potential. On this case, a creature may nonetheless be exiled, relying on the wording.
608.2b If the spell or potential specifies targets, it checks whether or not the targets are nonetheless authorized. [..] If all its targets, for each occasion of the phrase “goal,” at the moment are unlawful, the spell or potential doesn’t resolve. [..]
