Even though he had just two training sessions under his belt, United's club-record £37.1million new boy lasted all but the final seven minutes of Tuesday's 2-0 win over Cardiff City.
"I have felt comfortable at this club from the first minute," said the 25-year-old.
"Time has gone so quickly but the welcome has been amazing.
"The lads are really good and there is a great atmosphere."
The good news for United is that Mata is acutely aware there is still much more to come from him.
"To be honest I didn't train that much last week because of the transfer," he said. "I know I can improve."
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