Third-placed City travel to Hull on Boxing Day (17:15 GMT) for the first of their three festive fixtures. City have kept five clean sheets in the 21 games Stones has played for them this season. Two came against Steaua Bucharest in the Champions League qualifying round in August. Prior to those matches, Stones had played in only three European fixtures, and Guardiola feels the demands now placed on him take some getting used to. The former Barcelona and Bayern Munich boss said: "It's the first time in his career he played every three days.
"He has to improve but he's open and he has a lot of personality. When you play in the big teams, the character is there. I have no doubts John has that." City continue to be linked with a move for Southampton defender Virgil van Dijk, 25. The reported £50m fee is more than they paid for Stones, but Guardiola says any deal will not happen in January. He said: "It is impossible for him to come here next month. We don't want him now."