Foden's ninth league goal of the season secured the unconvincing 1-0 win that pushed champions City to one point behind Premier League leaders Liverpool.
With Erling Haaland not back to his best after injury and playmaker Kevin De Bruyne used as a late substitute on Saturday, Foden was the spark that kept City's bandwagon firmly on track for a fourth successive title.
Foden has also contributed seven assists this season and has stepped up to be one of City's leaders on the pitch.
"Forget about the goals -- of course they are important -- but do you know how he played?," Guardiola told reporters.
"How he controlled and accelerated. He has become already a top-class football player. From a little boy, now he has become already Phil, a world class, top player.
"He's so good. He can play everywhere, especially in the central position and play really, really good."
City are now 11 games unbeaten in the league and while Liverpool and Arsenal are right with them in the title race, Guardiola's side are showing again the ability to churn out results at the business end of the season.
They beat Brentford 1-0 in midweek and Guardiola said his squad's durability still surprised him.
"What can I say?, The calendar is so demanding and the expectations are so high," he said. "What they have done for many years with a lot of games and many things.
"And always you believe they will fall down and won't continue to do it -- they surprise me."
