You're probably right that Gurley is gone before 27 and you may be right that Gordon is too, but I don't think it is a foregone conclusion that it'll happen that way.
With the RB class being so deep and with how teams feel like they can find a runner outside of round 1, I could see San Diego going with OL or edge rusher at number 17. If you needed OL badly, would you rather take an OL in the first and then pick from Ajayi, Duke Johnson, and Tevin Coleman, or would you rather take RB in the first and then pick out of whatever is left over on the OL? I can't tell you what San Diego will do, but I can tell you that just about every NFL team will want to go with the elite OL and find a Eddie Lacey or Le'Veon Bell in the second round.
Now, we all know that Gurley is supposed to be special, so maybe they go ahead with a runner at 17, but I wouldn't be too surprised if they went somewhere else and took their runner later... particularly if you throw in Gurley's knee.
Frankly, if Dallas picked 17th, I probably wouldn't want them to take Gurley either. There will be guys like Dupree, or La'el Collins available that just make a ton more sense for SD there.
As for Arizona, they will have a very good WR or two staring them in the face, and probably a highly rated OL as well. If SD takes Gurley, would they take Gordon over somebody else? Maybe but I wouldn't bet the farm on it.
I could see Gordon or even Gordon and Gurley there when Dallas picks. I do think there is a good chance Gurley is gone though, but his knee gives me a small hope. Gordon very well might be there.
Man, the draft is taking forever to get here...