I'm also at level 4 and I still have 2 players of my initial team.

One of them is a DC/DR with Aerial defender SA and was my best player in the initial squad with 5 stars. He's currently at 4 stars/32q and is still one of my preferred starting 11. That's mostly because I haven't found decent replacements for both positions yet. I used to use him as a DC and now as a DR - he'll deffinately be a sub in my next season though.

The second one is an MC and I've just kept him because I only have 3 MCs and he turned out to be a fast trainer, although low in quality from the start and since the game likes to injure all of my MCs at once he has been recovering for a good total of 30 days. Needless to say - he's a reserve.

Used to have a DR that was an ultra-fast trainer, but that one got injured once per 3 games played or once at every 10 trainings ... even started with a broken foot since day 2 in the game. I don't believe I got to use him in more than 10 games - sold him at the end of my second season.