i am in need of a MR and ST, but wanted some tips when buying, now i wanna buy a 5 star player (MR or ST) , now should i go for players whose quality end in 4 or 9? and if so does age matter (i am looking about 18-22)

Also if there is a 5 star and is 18, and quality does not end in 4 or 9, does that still matter?