The Chile midfielder was outstanding for their derby win over Swansea City.
"Gary has been outstanding in terms of the way he has adapted to a different culture and settled into Premier League football seamlessly," said Mackay.
"He is having English lessons four times a week and is making good progress, he has been working hard on that.
"Those English lessons take time, but he is enjoying living in this city.
"He has settled in his house and knows where the better restaurants and shops are.
"All of that helps a player settle in."
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