The Rams have to be careful with this and I think they are.
Naturally the OBJ side wants a deal right now, and a good one that places as much risk as possible on the team and not on his own health or timetable.
So, it'll be an interesting Kabuki dance as they work through this.
I suspect the Rams know they hold a pretty strong hand. OBJ is not a WR1 any longer, and what team is going to sign him this early into rehab for the 2nd ACL in as many seasons on the same knee? Not that it couldn't happen (it would be something the slowly diminishing Cowboys might do).
I would imagine the Rams offer has lots of injury and performance incentives but is short on guaranteed money. And every player wants as much guaranteed money as he can get.