Get rid of them all. People can talk all they want about "bad luck" with prospect injuries, or how the team is improved over the last 3 years, but this is still a terrible baseball team. Yes, rebuilding takes time, but at the rate we've been 'improving' it'd be 2017 before we even have a chance to sniff a wild card.
On the pitching side we're 27th in team ERA, 26th in team WHIP, 30th in K9, 25th in opponent OBP, 27th in opponent OPS, 27th in opponent SLG. Remind me again why I'm supposed to be enthused about this? Exclude Hughes, and the rest of our pitchers are probably 30th in every pitching category.
On the hitting side, it seems like lots of people are conveniently ignoring how lucky we've been with some of our players. Sure, we've had some bad luck with prospect injuries, but as much as I want to see him in the bigs, Sano wasn't going to suddenly make this a good team on his own. Suzuki, Escobar, Santana have all played much better than anyone could've expected for much or all of the season. Vargas has been mashing since his call up. Sam Fuld played very well for a stretch. Dozier was on fire in the early goings. Our SS in CF experiment hasn't been nearly as disastrous as it probably should've been. And the list goes on. From the major league clubs standpoint, I'd say we've been quite a bit more lucky than unlucky, and the result is still going to be a 90 loss season.
Maybe I'm just too negative, but I don't see any way the FO can seriously look the fans in the face and claim they're justified in bringing back the exact same coaching staff after four years of this garbage. There isn't another org in baseball that would put up with this without making some significant changes.