Well I wouldn't call Neris "our closer." But yes, I agree, his value, due to having closer experience (and a lower salary) is probably higher than Neshek, Hunter or Nicasio.
The word is Robertson will pitch wherever leverage dictates, Neris and SD will see their share of 9th innings too I'm sure. Maybe Hunter as well (let's not forget how good Hunter was in 2017 and also that he wound up being pretty good last year, all told).
I think they are most down on Neshek because he is not that durable (either in terms of length or consecutive days) and has previously expressed a preference for being used predictably.
Robertson is not going to be a LOOGY but he's definitely the guy who will be pitching to Freeman or Soto (or, hmmh, Bryce Harper) if it's the 7th inning or later. The trick is to not let those guys come up again in the 9th if they're up in the 7th.