Dalbec is still on the roster because he's the only "natural" 1B they have. And yes, he is converted from another position so that is a weird thing to call him, but it's been his full time position in the majors. There are others with the flexibility to play there (Santana, Gonzalez), but they're not good full time fits. And more importantly, they're also not hitting any better than he is. So if you call up Duran and send down Dalbec, you're not solving the issue of who will play 1B. Renfroe is the regular RF and has started to hit decently. Verdugo has recently settled into LF and there is no way Duran would start over him. They must like Hernandez' defense because he's become the regular CF. If they think the delta in defensive value between Duran and Hernandez is big enough, he really wouldn't have a starting job to step into, and why call him up unless he gets regular playing time at this point in his development?
The reason to send Dalbec down is because we're actually in the playoff hunt. Right now Dalbec, Santana, Gonzalez, and to some extent Hernandez are all dead weight with the bats. Someone needs to go, and if it means swapping Hernandez for Wilson, while sending Dalbec down and playing Santana at 1B, so be it. We keep all the binkies in that scenario, even the crappy ones.
We just need to upgrade a couple of bats from abysmal to average-ish.
For position players on the 40 we have:
Noncontendors:
Connor Wong, Ronaldo Hernandez: catchers.
Jeisson Rosario, CF. AA. Not hitting well this year.
Hudson Potts (Injured)
Possible help:
Franchy Cordero, LF. Crushing righties, minimal but crappy exposure to lefties.
Marcus Wilson, CF. Knocking the snot out of the ball in AAA with no platoon split. And can play CF.
Jonathan Arauz, 2B, SS, 3B. Noodle bat with flashes.
Michael Chavis. 1B. Sometimes slighty worse than average is better than nothing.
If you dump/trade Gonzalez or Santana, OF Johan Mieses currently has a hot bat.