I also don't think Jackson's status is irrelevant. His being out makes it more likely that Gordon will suit up.
In the short practice clips I saw, Gordon looks physically ready to go. He's not obviously out of shape or anything. ("Game shape" is a real thing, but if he's not in game shape, that just means all of his leg muscles will be unusually sore on Monday. It doesn't mean his performance would be affected on Sunday.)
And I'd expect him to be mentally ready as well.
If Jackson were okay, I'd sit Gordon out on a short week (for him).
With Jackson out. I'd put Gordon in to take Jackson's role. (And I'd pay him, obviously. Since he didn't report Wednesday, the team wouldn't be obligated to pay him. But if you play him, you should definitely pay him. That was probably the deal when he showed up on Thursday.)