Murray is example 595 on why you normally should not spend a 1st on a RB. Or worse yet, the equivalent of two mid 1sts like we did.
Use them hard through their first contract and the last two years of it use a 3rd-5th rounder again in the draft to find a replacement. If they are really great, maybe extend them.
Look at the top 10-15 NFL rushing leaders every year...chock full of 2nd thru 5th rounders.
One contract 1st rounders can hurt. Later rounders, not so much.
Luckily, it looks like Dallas landed a monster. So it's ok