At NU, Fields played running back but quickly fell down the depth chart after his tendency to run backwards and not be as fast at running backwards as he thought he was, ending up losing yards as often as he broke them and going from a promising true freshman to a backup, unable to break into the running back rotation even after serious injuries only getting two carries after the loss of Mike Trumpy at Wisconsin and deciding to transfer a few weeks later. He was more promising in baseball - I'm not up on my SEC hardball, but I believe it's more baseball-friendly and that transferring to the ESS-EE-SEE will big up his potential of making it in the pros.
That said, it's definitely a move in the wrong direction football-wise for Fields. I'd be shocked if he plays his way into LSU's running back flow, just guessing from the fact that NU is desperate for backfield talent and he couldn't break in, while LSU is, you know, better than Northwestern. Fields had athleticism, but once he got on the field with guys who could run as fast as him, he lost all ability to do anything meaningful. He looked dominant sometimes against lower-tier teams, but couldn't do it against comparable competition.
Maybe I'm wrong, but I'd guess he'll be eligible to play baseball next year, probably, right, considering he hasn't played for our team this year, but will have to sit a year for football.
Bummer he didn't work out for NU - that said, Geaux Arby.