Machado injured his left knee while trying to tag up from second base on a fly ball. He fell to the ground, was tagged out, and had to be helped off the field. While the play initially looked bad, Dan Connolly of the Baltimore Sun reports that Machado did not appear to be in too much pain after the game.
Machado will have an MRI on the knee once the swelling goes down, hopefully today. MLB Prospect Watch will have more information on the injury as soon as it is released.