Messi has been linked with a move to Manchester City, including Paris Saint-Germain and among other top European clubs.
Barcelona on Thursday officially announced that Messi would be leaving Camp Nou as a free agent this summer.
Speaking on the development, Guardiola insisted that Man City will not sign Messi because they have already signed Jack Grealish.
“We spent on Jack Grealish and he will wear number 10 because we [were] convinced about him, and thought Leo would stay.
“Now Messi is not in our plans,” Guardiola told the BBC.