You can def help someone become faster and stronger with the right training regiment. Even technical ability can improve. Saka has dramatically improved his first touch and link up play since he broke into the first team. Those were the two things I had concerns about with him, but he is one of the best in the world at those two attributes for a winger nowadays. Martinelli has also improved his touch and control, he is still inconsistent with it, but he def has improved, he has also gotten stronger over the last year. We have even seen Nketiah get stronger and quicker. He was nowhere near the athlete he is today when he played U18 football.You can't coach someone to be faster or stronger, and I agree even technique is somewhat static. But you certainly can coach up a player's tactical understanding, awareness, movement, decision-making etc; in other words, how effectively they use their natural ability. Its easy to forget how much coaching and training is involved behind the scenes.