I would classify the idea of getting a first rounder for a RB going through rehab from a catastrophic knee injury as "unlikely".
I grant you, it would be difficult. Frankly, I am not sure what Barkley would command in return.
If not my ideal scenario, maybe a very good, but not all star offensive lineman and maybe a 2nd or 3rd or later round pick along with it , or at least one of these . In the pro basketball arena, the Nets signed Durant even with his injury. The Knicks gambled on Amare Stoudamire with his knee issue.
The fact that SB has had two serious injuries in successive seasons, might give a lot of teams pause as to what they would offer in return. Then again, the Giants out of pride, might not even trade him.