If you have young fast trainers, just dont lose any chance of training between matchs, thats what i do, and i hVe players that gaine 90SP season, even without spend greens, sometimes i just use a few greens If they are already near the next star.

As Khris said, some players will play good no matter the stars.
Last season my second Best ST was 3* with 18 goals in 22 games. My Best MC was a 31 years old 4* the weaker of all my MCs in Q.
My ML /AML is in His 6th season, he is now only 3* but in 3 games, 2 assists, as Been always one of the players with more goals scored.