He's calculating every move and doesn't try to run down some balls that he might have otherwise tried to reach. But his serve is working at least and Bautista-Agut is not playing very well. It's so frustrating to see because a healthy Ernest would definitely have beaten him. But today... he is very vulnerable at the moment because of his limited movement.
Edit: it doesn't seem like it's the ankle judging by the way he bends his knees often. And now that his serve wasn't working he lost the break. Damn... I can't watch it, it's obvious something is bothering him