During the current campaign, Sane has contributed six goals and nine assists in the Premier League, while the German international also played a key role in City's 4-1 victory over Burnley in the FA Cup on Saturday.
However, despite emerging as one of his key players at the Etihad Stadium, Guardiola has called on the winger to improve his performance in defensive areas.
The 46-year-old is quoted by the Manchester Evening News as saying: "I said to him many times I don't have doubts how important he is for us because he makes runs in behind but there's still a lot of things to improve. Leroy makes mistakes in the simple things - big mistakes. He has a lot to improve.
"He is a special talent, we need his goals, but it's how he defends, [goes] backwards, but he's only 21. I knew only one player (Lionel Messi) who could do everything at that age - the other guys have absolutely many things to improve."
Sane could feature when City face Bristol City in the first leg of their EFL Cup semi-final tie on Tuesday evening.