Despite evidence to the contrary being around since 2012 (thanks again Shrewnaldo and Maestro Ugo), there are still plenty of people who believe that players with high Determination and/or Work Rate attributes develop their current ability faster because they apply themselves better during training sessions somehow. After all, if someone is determined and works hard then surely they will reach their potential faster, won’t they? As you may have guessed, the title being a dead-on giveaway, this is not the case.
Just to re-iterate my point; the attributes Determination and Work Rate only apply within matches. These attributes contribute nothing at all to the development of a player during training sessions. The driving factor behind the development of youngster is the Professionalism attribute.