City sit just fifth in the Premier League table after 21 games, though, and are already trailing leaders Chelsea by 10 points, with last week's 4-0 humiliation at the hands of Everton sending alarm bells ringing.
But Rummenigge believes it would be wrong to criticise Guardiola and says City have no option but to enter the transfer market.
"You cannot blame Pep for anything. Manchester City will be patient," Rummenigge told Bild.
"They have no other option but to enter the transfer market and bring in some quality players in order to give Pep the chance to be successful.
"There is not as much individual quality at Manchester City as at Barcelona or Bayern."
But Rummenigge has warned Guardiola that Bayern have no intention of selling any of their star players.
"We will keep all our best players here and not allow anyone to leave," he added.
Rummenigge feels City's lack of individual quality is not Guardiola's only problem, though, and has suggested he faces a tough task to stay true to his own philosophy.
"Things have become much more difficult in England because all clubs have invested a lot of money," the Bayern supremo continued.
"And things are more complicated at Manchester City than at Barcelona and Bayern Munich. There is a different football culture in England. It is much more physical and all about kick and rush. That makes it hard to stick to Pep's philosophy."