Obviously we still do not see the best of Alexis and that is something very promising. He has an incredible work rate, always wants the contact with the ball to influence the game. Hopefully that spirit will spread to the rest of our team.
About the penalty ... after all the fault and what he ran it is understandable that he does not kick it well. Maybe he thought "the rival team does not hurt us and I've done a good job - I deserve a gift". Probably Mou will give the penalties to Pogba and the freekicks to Alexis.
Mou needs to establish a role for him. Maybe now he plays like LW to better assimilate our style of play. I do not think he has this position permanently. I prefer him as RW interacting with Valencia or behind Lukaku.
A chant for our little friend:
Alexis Sanchez, at No 7,
He is our chilean hero,
Signed from Arsenal on a free,
He cost us fecking zero,
He was tempted for Man City,
Until Jose came calling,
He took a look at our history,
And left bald Pep bawling.