Did your trainee get in foul trouble? I wouldn't use the sit them in case of foul trouble option.
nope, they have less than 2 fouls per game...and I wrote wrong in previos post, I use let them play instead sit them...
other thing that cross my mind is low stamina, 3, 3 and 4, but players from other managers have better stamina, and same problem...
also, I have lvl7 trainer, and training stamina is not an option for now, all 3 of them are top U20 prospects, and there is no time to waste in this stage of their career (18, 19 and 20y old)...