The noun "expertise" defines, according to Oxford Advanced Learner's Dictionary, expert knowledge or skill in a particular subject, activity or job". It is no wonder, and for appallingly obvious reasons, that "expertise" is not considered part of vocabulary used when defining John's skills. To the contrary, John's only expertise centres around poking fingers at various holes on server boxes. No doubt about that.
John excels marvellously at managing inventory control jobs. Be it making sure which systems go where, or counting the number of laptops lying on top of a wooden closet so that the figure tallies with the previous one, John is unbeatable. He is unparalleled. The peons hold him in much respect. Last someone checked, John knew full well how to load papers on a printer, too. Hmm.
John leverages a couple of advantages at his job. Sensing trouble against his servers, John always has the option to shut all his servers down, lock himself in the room, and sit on a chair, prespiring, without even running into so much as a danger of being reprimanded for causing network downtime and consequential losses — never mind the fact that he almost always gets away with it with impunity.
John possesses an impressive sixth sense. He can sense danger from a kilometre. And when he sniffs trouble [from a kilometre, that is], he makes sure he does what he thinks is right and sufficient to thwart that trouble, including, as is on top of his list, shutting down everything and waiting for the thunderstorm to come and pass. That the thunderstorm never comes, that it never even existed in the first place is besides the point.
In loving, breathing memory of John, the proud, good-for-nothing Network Manager.