The 23-year-old has enjoyed a fine start to life in England since his summer arrival from Benfica, bolstering a City side which currently boasts the best defensive record in the Premier League.
Indeed, in Dias' 22 appearances, City have kept 14 clean sheets and Guardiola is understandably delighted with his new recruit, whose qualities he feels are rare for someone his age.
“[His impact] has been massive,” Pep said at his pre-match press conference ahead of City’s game against Aston Villa.
“He is always concentrated, doing what he has to do and helping his mates - holding midfielders, full-backs and central defenders - always be concentrated.
“That is not easy to find in a 23-year-old.
“We knew the quality on the pitch. We knew the personality he had, but of course we are impressed with the mentality and the physicality to play every three games.
“Always you expect the best, but we are more than delighted with his behaviour and what he provides for the team.”
Dias’ partnership with John Stones has been one of the highlights of the current campaign and in the 10 games the pair have played together, City are unbeaten, winning nine and conceding just once.
Stones, who scored his first Premier League goal for the Club against Crystal Palace, has enjoyed something of a renaissance after being in and out of the side last season.
Guardiola says it is the defender, not the manager, who deserves credit for his performances and has challenged the 26-year-old to take the steps to ensure he maintains his current form.
“I have said many times, when a player is playing good consistently, it belongs exclusively to them, not the manager,” added the City boss.
“It is a long process. The consistency must be for a long time, not just one or two months.
“John has done well in the last two months, but for a long time he was not regularly playing, and for many reasons.
“He has to be consistent in his life, take care of his body. Not just John, everyone, because the schedule is so demanding.”
Stones has earned widespread praise for his performances this season and he has benefited from an extended run of games after an injury disrupted 2019/20.
Many have suggested the Yorkshireman is playing with a newfound confidence, something else that Guardiola says has come from within the player.
“The manager is not the guy to say one word and the confidence is back,” he explained.
“The confidence is back when you live your profession 24 hours, train really good, eat really good, rest really good. The rest of the qualities will make the difference.
“Understand the way we want to play, have a good relationship with your team-mates, that is the only secret.
“It is not that I will give you confidence right now because I spoke to you for half an hour. The confidence comes from the player himself.”
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