Unfortunately, there is no good answer to this age-old question. This, and goal line surges, is what makes working the wings so very difficult. I have ALWAYS said the two wings do more than all of the rest of the crew combined. I believe that.
When speaking of "areas of responsibility," which, in the NFL, at least, has nearly replaced the traditional concept of "keys," the deep guys need to be able to shift their attention to this action, and be able to make rulings, or, at least, assist in making rulings like this.
Beyond that, you just simply have to do the best you can to know where the receivers are in your area, and what the BC (passer) is doing. Yep, a lot of head-swiveling.
When I worked L, I would work at the back of the white, as much as possible, and wider when we got outside the team areas. That helps by relieving a lot of the concern about running for your life. I know some guys today are preaching working right on the sideline, to ensure a good view of catches at the sideline. I'm not convinced. If you keep your restricted area clear, you can see see the sideline well, anyway. And, you usually have time to move toward the sideline and get a great angle down the sideline.
You are in the same company with every other wing guy working American football. Good luck.
