Manchester City have opened discussions with Everton over signing England defender John Stones, according to reports.
City are currently in China on their pre-season tour but continue to be linked with a series of big-money transfers, with the Toffees centre-half said to be top of their list.
Leonardo Bonucci, Leroy Sane, Gabriel Jesus and Marlos Moreno were all said to be City targets on Wednesday, but various reports suggested they are closer to bringing in Stones.
Stones, 22, has previously been coveted by Chelsea but new City boss Pep Guardiola is giving close attention to his back four given Vincent Kompany's injury record and uncertainty over Eliaquim Mangala's future.
Everton would value Stones at up to £50million in the current climate, with fees significantly inflated since last summer when he was rated at £40millon.
Everton were unavailable for a response when contacted on Wednesday night, though Guardiola had talked about his defence at a press conference in Shenzhen earlier in the day.
While Stones was not mentioned by name, Guardiola described his preferred centre-half as one who could bring the ball out from the back before making a transparent reference to the transfer window.
"We need to create good build-up play, with easy passes in midfield, to achieve good passes for our strikers further up the pitch," he said.
"I believe when the ball goes from a central defender to a striker, the ball comes back as quickly as it goes, and we have to make it clear that we are building up in our first process, whether that is defenders or midfielders.
"That is why we need players of quality, to play in that style, and we have the players to do that.
"By August 31, we will have the right players to play the way we want."
The former Barcelona boss has been known to use midfielders in the back four, most successfully converting Javier Mascherano, but his suggestion that the likes of Fernando or Fernandinho could be utilised in a similar way could just as easily be seen as a veiled plea for reinforcements.
"Fernandinho can play in 10 different positions because he has the quality to play wherever," he said.
"He is quick, aggressive, intelligent and strong in the air.
"He has the quality to create good build-up play and can play a forward pass, so I think he has the quality to play there (at centre-half).
"Fernando can also play there, but maybe he is not as quick as Fernandinho. So at the end of the window, we will have to see which players we have."
Kompany is set to sit out the start of the season with a thigh complaint, leaving City on the lookout for a replacement skipper.
And Guardiola is happy to leave that decision to the dressing room, having yet to make his own appraisal of who should lead the side at the start of the campaign.
"Vincent is the captain, and when he's not playing, the players have to choose," he said.
"They have to decide who the real captain is for them. I have never believed I should pick the captain, because I am not in the locker room, not in the dressing room, I'm not in the meetings when they believe they have to change something.
"They have to choose for themselves the best guy to represent their opinions. I don't like to do it, because I have only been here a month, so they must decide. It's their responsibility.
"We've only been together a few weeks or a month and they know each other better than me. It's their responsibility."
Guardiola also stressed his hardline approach to fitness and conditioning following left-back Gael Clichy's claims that he had banned pizza and banished individuals from first-team training for not hitting their weight targets.
"Normally I'm not a guy to say 'you can't eat that', I don't know what they eat normally. They eat what the nutritionist decides," said Guardiola.
"They were not overweight (at the start of pre-season), but I want my players fit. For me, weight is so, so important.
"We need to run, we need to fight... after three days (do it) again, after three days again, three days again.
"When you are not fit and your weight is not proper, danger is coming. That's why I want my players absolutely fit."