Stones is set to come up against former club Everton for the first time on Saturday after his big money move in the summer.
Everton are now managed by Guardiola's former Barcelona team-mate Ronald Koeman, who the Catalan coach rates as one of the greatest of all time.
Guardiola says Stones is not quite the finished article just yet but he feels the England international has the potential to become one of the great central defenders if he continues to improve.
"It's quite similar in that they both like to play the ball," he told a news conference. "Normally a central defender is a big guy, good with their head, mark man-to-man - and we need that, of course. You need central defenders for that. But now it's a plus if they've got the quality to play.
"John has similarities to Ronald. Especially in the mentality. John is a guy who always wants to play, be under pressure. Normally the players who like to play the ball handle the pressure better than the other ones. I cannot compare them still now, not yet, maybe in the future.
"The long balls of Ronald - he was the best ever. But John is young enough, he can improve.
"He played with the national team very good. In the last European Championships he didn't play one minute and now he's playing all of the games. He's already he's an important player for the national team and I'm so happy for that."