Stones has made just 12 appearances for City this season and has not played since picking up a hamstring injury in last month’s derby defeat to Manchester United.
The 25-year-old was available to Guardiola for the victory over Everton on New Year’s Day but failed to make the matchday squad, with teenager Eric Garcia preferred to play alongside Fernandinho and Rodri in central defence.
Guardiola believes Stones is improving in training but called on the £47.5m signing to maintain his fitness in order to win back his regular starting place.
“Step by step he’s getting better, he’s still not at the top but he’s good for some minutes for tomorrow,” the City manager said.
“He has to be fit, after two or three games he fell down and he cannot play. We tried to hep him, we tried to do the best to help him since the first day of the three and a half years we are here. We do everything for him.”
Guardiola said he still has faith in Stones but was more cautious when asked whether the England international has the ability to be the country’s best defender.
The Catalan claimed he did not know why Stones has struggled for fitness and form over the last year. “He has the conditions to do it, but to be the best central defender you have to play one entire season, every three days being there,” he said.
“It’s difficult to reach the potential that he has, he has to be at the level to play regularly. The last three seasons and a half he could not do it.
“It’s difficult to know the reason why. Sometimes when you have a tough injury, for example like Aymer had this season or Gundogan in the first season, sometimes it’s unlucky, or Mendy the year he arrived, first year he arrived. That can happen, you know, it’s unlucky.
“But in the case of John I don’t know. I don’t know why he is not able, we are not able, to be a regular for a long, long period because he’s a young player.”
“He’s still young. As a player he has his future in front of him, it depends on him. It’s in his hands and in his head to become one of the best.”
Stones will play a part in Saturday’s FA Cup third round tie against Port Vale and will come up against target man Tom Pope.
After Stones’ calamitous display in England’s Nations League semi-final against the Netherlands last summer, Pope tweeted that he would fill his goal-scoring boots if he played against the “weak as p***” City defender every week.
“I know I’m a League 2 player, I know he plays for England, I know he’s on £150k a week, I know he’s a million times better player than me but I’d love to play against John Stones every week,” Pope said. “I’d get 40 a season!”
Guardiola only learned of Pope’s tweet when it was relayed to him on Friday afternoon but simply said it “was not nice”.
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