Barbara, Costa's technique isn't as bad as you make it out to be.With his great physical attributes he is also able to combine his ball skills with his strength,in many of his goals he shook off the defender before he shot. And consider we have many player in our squad who are good on the ball like Hazard,Oscar,Willian,Fabregas or even Matic who also has decent technique.Costa also fits very good in Mourinho's counter-attacking system.