Maguire, who was heavily linked with a move to the blue side of Manchester has completed his move to Manchester United.
And divulging the reason why the Citizens failed to land the bulky defender, Guardiola disclosed City were far away from Leicester City's valuation for the 26-year-old defender.
“Maguire is an excellent, top-class player," said the City boss after beating Liverpool on penalties to lift the Community Shield.
"We were interested but we could not afford it. United afforded it.
"He's an excellent player, he made an incredible World Cup (in 2018), he's strong in the air, good with the ball in the build-up and he's so fast.
"Congratulations for United for this signing.
"I don't know if it will be like last season, two real contenders - Liverpool and us - to win the Premier League.
"I think United with Maguire and the other players they bought, Arsenal as well, and Chelsea, and Tottenham that they won all the pre-season so I think there will be many, many contenders this time."
After the revelation of how City missed out on Maguire, Guardiola believes Liverpool's performance in the Community Shield was superb.
"They are a top-class team and the difference is one point ahead and one penalty ahead, that is the difference. It's minor," he said.
"Sometimes the coin can come on your side, sometimes it cannot so that is why it's good to face them to see how prepared we are to win the title."
