My sense, from reading his article, is that the difference between the senior and the competent levels has much less to do with technical knowledge and much more to do with experience, judgement, people skills and maturity.

If you're picking a guitar player for a concert series, getting someone who can play proficiently is only part of the problem (there are plenty of those). You need someone who is reliable, consistent, emotionally up to the rigors of the road and nightly performances, someone who will reduce friction among the band members and not drag in issues of his own. In short, you need the same characteristics as the senior dba.

I might add, that there is really NO way to test for these characteristics for either the guitar player or the DBA. You can rule out obvious clunkers, but a trial period is the only way to see if you're a good fit.