Specific Weakness - Important Matches

[distant sounds]

I recently signed a wonderkid forward who has very promising stats for a 20yo. I didn't notice when signing that he has Important Matches as weakness. I normally check the weaknesses before signing a player but forgot to this time. He played well second half of last season getting 10 goals and 6 assists from 17 starts. But I did notice he struggled in the big end of season games and I had to sub him less than an hour in. Is there any chance this weakness can improve say with age? With no ability to tutor on FMC, does the training help with it at all? Am I going to be stuck with a great player who does well in normal matches but will always struggle in big games?