John Stones' inability to stay fit has denied Pep Guardiola an ideal defensive midfield solution, caused Manchester City to spend £63m on new centre-backs and forced Pep Guardiola to play Abdukodir Khusanov ahead of schedule against Chelsea.

That is the damning verdict of Guardiola, who has challenged Stones to make himself available in the Champions League this week to help the squad after missing large portions of the last two seasons due to recurring injuries.

Stones has struggled to maintain his fitness this season and hasn't completed 90 minutes for City since the end of October. He has been injured or unfit for 15 of the last 19 games, with three separate comebacks halted after a single game. The 30-year-old has missed more games this season through injury (15) than he has played (14), following on from 14 games missed last season through injury.

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On his latest return from injury, Stones came off the bench at Paris Saint-Germain and was introduced against Chelsea to end the nightmare debut of Khusanov before the hour mark.

Guardiola stated that Khusanov 'shouldn't have played' against Chelsea as a young, new signing, but Stones' injury record made it necessary, and outlined why he feels he cannot play Stones as an alternative defensive midfield option.

City have spent £63m on new centre-backs this month, and Guardiola also insisted that wouldn't have been necessary if players like Stones and Nathan Ake had better injury records.

"John always had these kind of situations - except the year of the Treble when he was incredibly reliable," Guardiola explained. "It’s the same with Nathan and that’s why we went to the market. I wouldn’t like to go to the market in this period but we have a lot of examples of [players] not being able to go every three days. This is the problem.

"Our process is not good because Rodri is not there. Manu [Akanji] played really good there and John too but Rodri was there alongside them. It’s not because I put you here, you played good there in the past. Before it was a process that was clever, easier.

"Now with John I’m struggling to see it, due to injuries, that he plays there. I prefer to see him back because as a defender, especially reading situations, he is so, so good.

"I have no doubts on John or even Nathan but they have not been here. And last season they have not been here either, so this is the problem. There are players who are reliable and players who have more problems than others. Hopefully now this time he has recovered better. We gave him more time.

"He played really good in this 40 minutes and has to make the effort for Wednesday, to give time for Ruben and Nathan to come back."

Guardiola added that Stones 'has to play' on Wednesday against Club Brugge in the Champions League where only victory will ensure City qualify for the knockout stage, with Khusanov and fellow new-boy Vitor Reis unable to play and no sign of Ruben Dias or Ake returning.

Meanwhile, winger Jeremy Doku will be out for 'a while', and will definitely miss the Club Brugge fixture with injury.