The Premier League champions dispatched Steve Bruce’s men 4-3 in their first game since being crowned kings of England.
The Spain youngster’s treble at the Saint James’ Park made him the youngest player to score three times in a single game for a team managed by Guardiola, eclipsing Lionel Messi in the process.
Torres has had to bide his time to make an impression since securing a £20m move from Valencia at the start of this season.
The 21-year-old made the most of his rare start and his hattrick took him to 13 goals in 34 appearances across all competitions.
"It's his first season in England and his numbers are exceptional," the City boss told Sky Sports. "He came as a winger, but he has had to think about being a striker. When Sergio Aguero and Gabriel Jesus were out, he was there.
"He didn't have minutes, but when he played he had a sense of goal. I'm really pleased.
"He can be [a number nine]. We will use him, we used him and he was brilliant. His rhythm, especially defensively, has improved a lot.
"The movement he makes as a striker. The [third] goal hits the bar and he knew where it would go. Strikers know intuitively where it will arrive. He has this talent, the first goal is fantastic."