Pep Guardiola has admitted it was a "surprise" to get the opportunity to re-sign Ilkay Gündogan.
The German midfielder has returned to Manchester City after spending last season at Barcelona.
Gündogan has signed a one-year contract at the Etihad Stadium with the option of another year and Guardiola said the chance to bring back the 33-year-old was "unexpected."
"Most of the time all the managers say in the transfer window anything can happen so this is the real proof," Guardiola told a news conference on Friday.
"It was a surprise, unexpected. We know him quite well; the staff and players.
"We know the quality he plays last year at Barcelona. High, high level.
"We didn't have any doubts when the possibility was open and we're delighted he is back."
Gündogan has agreed to write-off the two remaining years of his Barcelona contract to return to City on a free transfer. Sources have told ESPN he also received interest from Saudi Arabia, but his preference was to return to Manchester.
"The important thing is he wants to come back," Guardiola said. "I got the message from [sporting director] Txiki [Begiristain] that Ilkay wants to talk to you and call you. He called me and asked about the situation.
"I said yes and now we are here and he has to deliver a good season.
"The feeling is that he doesn't come to retire or to remember good memories. We have time to do that in the future. Now it is time to put your shoes on and do your best."
Gündogan is City's second signing of the summer after the arrival of Brazilian winger Savinho. The club, according to sources, are still looking into the possibility of bringing in another attacking player before the window closes, but the clock is ticking ahead of the Aug. 30 deadline.
"I don't know what is going to happen," Guardiola said. "Could happen something in terms of injuries; hopefully not. Right now I don't think so."