Pep Guardiola is frustrated by the decision not to award Douglas Luiz a work permit, with Manchester City having hoped the Brazilian midfielder could provide cover for Fernandinho.
The 20-year-old spent the 2017-18 season on loan in La Liga with Girona, making 15 league appearances but only starting one of them, after joining City from Vasco Da Gama.
Brazilian Douglas Luiz featured in pre-season for City, who failed to add a deep-lying midfielder to their squad after Jorginho opted to sign for Chelsea rather than join the champions.
And Guardiola could not hide his annoyance at the timing of the decision over Douglas Luiz's work permit, which gave City little room for manoeuvre in the transfer market before Thursday's deadline.
"We'll try to help him go on loan again and get the work permit," Guardiola said at Friday's news conference.
"It's difficult for me to understand, one guy who doesn't see him in training has to judge. He has the quality and ability but I accept the rules, even though I don't understand it.
"The Brazil manager [Tite] and myself know more but it is what it is. I am sad and disappointed as he could play with us, and the reason why we spent so much to buy him is he has a huge capacity to play with us, we work a lot with the work permit as we believe he can play.
"We decided to play him [in pre-season] as we believe in him, but they didn't know him, no one game or training session. I don't understand but I'm in England and I can accept it.
"I'd rather it was announced 10 or 15 days ago, maybe then we can decide what to do. One day before end of play [transfer window closing], I don't know, he's not tall enough or didn't play enough games in the past or the price or something, OK."