The Spanish coach, who has already made it clear over the years he has been with City that he does not hesitate if he has to let go of players who are not 100% committed to the club, did not mince his words.
When asked about Atletico's target, the Argentine striker, he confirmed that Alvarez will be red and white. "He played an important role and we are grateful to him. His behaviour was incredible, but he wanted to leave, a new challenge and Atletico Madrid is one of the best teams in Spain and Europe," he said of the Manchester City player.
But Guardiola added: "Why should he stay if he wanted to leave? We wish him well. Julian thought his time here was over and the two clubs came to an agreement," he said.
New challenge
Manchester City followed up the treble with an unprecedented fourth straight Premier League title last term and Guardiola has set his sights on more records.
City face United at Wembley in a repeat of the FA Cup final, which they lost 2-1 to their local rivals, and Guardiola said they will give their all to win the trophy.
"It is important, it is a final against United, a part of that is trying to refine ourselves. It is step-by-step. (It is important to see) how young players behave on the biggest stage. We will go for it," Guardiola told reporters on Friday.
The Spaniard's name has been linked with the vacant England job after Gareth Southgate resigned last month. However, despite his contract with City running out next year, Guardiola said he was focused on the present.
"I have to decide what I want to do in my life — (whether to) continue here (at City), take a break, a national team, anything. Of course, right now, I am here," he said.
"My energy rises again, I'm fully excited for the season. We will see, it's a new challenge to break our own records, we will see the ambition in ourselves."
