Foden took up the playmaking role in the absence of the injured Kevin De Bruyne, who is out for several months after surgery.
He created seven chances from open play, including the winner for Julian Alvarez. This total was his highest in a Premier League match, in his 131st appearance in the competition.
“Phil [Foden] is a reality as a player,” Guardiola said. “He can play many positions. He is a real threat. I am really pleased. The way he behaves with everyone. The mentality is always there. That is the most important thing.”
Guardiola also singled out the mental strength of his Man City side who had come back from their UEFA Super Cup win over Sevilla late on Wednesday and beat a Newcastle team whom he views as title contenders.
“There are no words to express my gratitude for the performance we gave,” Guardiola told BBC Sport. “It was really, really good.
“It is the second game [in the league] but after what we done in the last season, we are still there.
“We spoke about mentality. The reason we won was about our mentality and we proved it again.”
At one point during the second half, Guardiola was seen gesturing and speaking to a fan in the stands, who was frustrated at the manager not making a substitution.
“He said to me, ‘Make a sub.’ I said, ‘Come sit here and do it.’
“The game was in a good tempo, a good rhythm. I didn't see the players too tired. It wasn't easy to make the changes so I didn't do it.”