Connor
The higher the driver level, the slower they will train.
A 5 ? driver will train much slower than a 1 ? driver but the more you train the driver, the stars will eventually increase.
However, if your manager level increases, the stars on drivers will decrease.
A 5 ? driver has the exact same level as your manager level.
If the stars go red, the drivers level exceeds the manager level. This means that training will be significantly slower, but you can still use that driver in races.
So I have 2 4* drivers, and one progresses quicker then the other when training, so it seems, but thanks for clarifying, that makes sense