I have had the sprinter story once. Only been through 1 season and 5 games though.
The storyline players are supposed to be randomly generated. I think I read that somewhere.
The DB was rated a 75. He is now a 84 through 5 games in the regular season.
WR was rated a 71. He is now rated a 77 through 5 games. Awareness is very low for him so when I raise that I expect him to jump up to the 80's. I never do pay much attention to the overall ratings though. Blackmon actually went down to an injury at the beginning of my week 4 game. This WR has been taking a large majority of the targets now. He is still second in receiving yards because Andre Johnson is having a beast year but he did jump up to third in receptions.
The DB has been on fire the past two weeks as well. He has posted three interceptions in two games. One of those picks went for a TD. Two of them came off of Tom Brady. Not many passes go his way anymore though. I am now upgrading his speed, acceleration, and agility so he can keep up with the speedsters in the league. He is already fast but I want him maxed out. I may scrap that idea and upgrade those things later in his career if I notice any deficiencies in his play that are easier to upgrade.