He is a very odd one, our Marcus. If you watch our 1-0 defeat to Arsenal, he made a very good pass to Mason, but then he will misplace the simplest of passes. He can actually destroy any fullback 1 on 1, but he is not the most consistent dribbler. He has a powerful shot in him and can pull of some miracle strikes, but other times, his attempts are comically bad. I actually think he offers more than Mata on the right, but he has been unwilling to track back and help the defence out since his return from the back injury. You can always see Mata/Mason tracking back and helping the defence out. I don't know if it's a consequence of his back injury or a tactical instruction to stay up for counters.
Either way, when Amad comes over, it will be interesting to see how Ole handles him, Rashford, Cavani and Martial.