Scott Willis has calculated Mkhitaryan's statistics.
The stats that show the Armenian’s influence are xG Chain and xG Buildup. He led the team in both, by quite a distance.
Expected goals (xG) are a calculation of how likely it is for a player to score based on various factors, such as the distance and angle of a shot from the goal, the number of players between the shooter and the goal, the manner that the ball was played into the shooter, and so on. From those factors, statisticians calculate how likely a player is to score that chance. If they’re 50% likely to score, the xG for the chance is 0.5. xG Chain credits everyone involved in the build-up of that chance with 0.5 xG. So if Mkhitaryan passes to Aubameyang, who crosses to Ramsey to shoot, all three of them get the same xG added to their xG Chain stat. xG Buildup does the same thing, but without giving credit for assisting or taking a shot, to shift the focus to build-up play alone. In the above example, only Mkhitaryan would be credited in xG Buildup. Source.