In extra-time he looked lost in some moments, especially with his passing when asked to take the initiative which let him down a couple of times. This is to be expected though seeing as the other players around were also mainly youthful and lacking experience and he is a 19 year old making only his second appearance on such a huge pressure cooker situation. By far the biggest game he has played in his whole life under such intense circumstances. All of which needs t be taken into account when assessing his performance.
However there were some good points as well, especially his desire and work ethic which cant be knocked. When he was brought on with a job to see out the remainder of the game he made some fantastic blocks, interceptions and tackles that played a big part in so nearly getting us over the line. He showed enough glimpses to suggest there is the potential of a very good footballer in there, even if its one that may never have the quality to have a career at United.
Nobody should be surprised he was brought on over Lingard either. Lingard is far better on the ball but much weaker defensively and physically, which is also why Macheda was brought on instead of him later on.