Kournikova lost her serve, became a double fault machine, not sure what concentrating would have done, it was more a form of yips. too much too young, as I'll mention later. She was still World class at every other aspect of her game. Think she served 23 d-fs in one match and still won.
Anyway I am hopeful for Emma, partly because she's played little tennis to this point, the entire phenom thing of having kids play a ridiculous amount of tennis early on, and leading to injuries and burn-out, is something she's avoided wonderfully, now she has a situation for about 8 months she has no points to defend, so she can carry on having a sensible schedule, and moving up the rankings.
If you compare her to our last great hope, Laura Robson, Wimbo junior champ at 15, basically retired now because her wrists are ****ed, possibly through playing lots when her body was developing.