Man City's Guardiola says De Bruyne can raise his game further
City forward Erling Haaland's double put the second-placed side up 2-0 on Saturday but Leandro Trossard pulled one back for the visitors before De Bruyne settled the contest by curling a shot from distance high into the net.
It was De Bruyne's second league goal of the campaign and he has provided nine assists, but Guardiola said there was more to come from the midifelder.
"Kevin can be better. He's not playing at his top level, not yet. He made a fantastic goal, but he's not playing his best," Guardiola told reporters. "He knows. I don't have to tell him. He's not perfect, he knows that."
Guardiola said De Bruyne's strike meant that City did not have to endure a nervy finish to the game as Roberto De Zerbi's Brighton threatened.
"The goal is outstanding," Guardiola added. "Thanks to him we didn't suffer in the last 15-20 minutes when the game was more open. The way Brighton play is outstanding. I'm a big admirer of De Zerbi and the way they want to play.
"The players felt...how difficult it was in the second half. The turning point in the second half was when Riyad Mahrez had a chance - and normally he doesn't miss it - but because it's football it happens. One minute later we concede a goal.
"In that situation the emotions are there against a difficult team. In that moment they were better, and Kevin made a master-class action so we win the game."