The City striker bagged three goals against Aston Villa to become the record overseas goal-scorer in the Premier League as well as moving ahead of Alan Shearer for most hat-tricks scored in the division.
The Catalan boss paid tribute to Sergio the man as much as Sergio the goal-scorer, saying he is “an incredible person”.
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“He was a legend already and that legendary status became bigger tonight,” said Pep.
“I think he is one of he most incredible players I have seen in this league.
“I think he is proud of what he has achieved and we said congratulations in the locker room, because to score this amount of goals as a foreign player and score so many hat-tricks means that for many, many years you have done good things.
“To achieve this, he had to be consistent for many years and this is an incredible compliment for him.
“The most important thing is that he is an incredible person - you cannot score this many goals or break so many records if you are not somebody is happy to be with his team-mates.
“He has to always be fit to be at his best and he sometimes needs a bit of time after he has been injured or in pre-season, but he loves to play football and he is a guy who when he is in the final third always has a goal in his mind.”
Asked whether his opinion of the Argentina star had changed since Pep first arrived at the Club, he said: “I had a good opinion of him when I arrived, but you have to get to know players and I was surprised to find out what an incredible person he is and I love to work with nice people - and he is.
“In the beginning, I had to try and let everyone play and that meant sometimes he didn’t play – and Sergio was never on the bench before I arrived here – so some people were surprised at the relationship we had when I first came to City, but now, it is almost perfect.”
And reflecting on City’s overall display as the champions dissected Aston Villa 6-1, he added: “It was good. From the beginning we were always in control. We made a lot of transitions and short passes and it was a great result and good performance.
“We played well against United, but they played better in the second half - today it was for the full 90 minutes.
“I think we have always been there this season, even when we have lost games like at Norwich, we created lots of chances - but sometimes maybe we lost our incredible focus occasionally and after back to back titles, it is difficult with the reality of everything.
“But now we are second and we are going to try and maintain this position until the end of the season.”