Dominic Thiem appears to have a new forehand. Thiem had to sit out for almost 10 months due to an elbow injury. The changed forehand could be an effort to protect his wrist. The new action uses the whole arm and his body to generate head speed. Previously, Thiem used his wrist to generate power.
It’s not uncommon for players to change their actions after an injury. Novak Djokovic changed his serve after an elbow injury. Juan Martin del Potro changed his backhand after a left wrist injury. Roger Federer and Rafael Nadal have also changed their forehands significantly over their careers.
Dominic Thiem is still early in his return to the tour. It remains to be seen how the new forehand affects Thiem’s game.