Some managers specialize in predicting player's subskills and buying the ones that are very close to the next level. They try to make that player pop in just 1 training and then selling him for a good profit. These people are known as skill traders
This is not to be confused with daytrading, for skill traders actually field players or buy players that played on the right position that week with their former club so they get training at their new club. On the other hand, skilltrading is closely related to daytrading as the main goal of both practices is extracting profits from the Hattrick-market imperfections.