Mahrez captained Algeria to the AFCON title on July 19 but returned to start against West Ham in City's Premier League opener, providing two assists in a 5-0 win.
Raheem Sterling helped himself to a hat-trick at the London Stadium, while Gabriel Jesus and Sergio Aguero also managed to find the net.
Guardiola was delighted to be able to call on Mahrez as he revealed Silva, a star of last season's title success, was left on the bench due to "little muscular problems".
"Riyad called me after they won [the AFCON]," Guardiola said. "He said, 'I need just 10 days. I want to come back soon. I want to play'. I like it. That's why I decide, 'Okay, I want to play him'.
"Bernardo had done nothing wrong, but there was some little muscular problems.
"I want them to know I trust all of them. That is the truth. After four seasons, I don't not like one player who is with us. I trust with them and they have to compete with opponents and with each other."
Guardiola's side returned to the top of the Premier League with their comprehensive victory, leapfrogging Liverpool, who beat Norwich 4-1 at Anfield in the 2019-20 curtain-raiser on Friday.
City will be gunning for a third successive title success this term, while also competing for silverware across European and domestic cup competitions.
From West Ham's side, the post-match narrative involved complaints of City's apparent tactical fouling, with Manuel Pellegrini attributing this to his team's lack of creativity.
Jack Wilshere had no issue with City's tactics, suggesting West Ham need to learn from such elite opponents.
"That's football," he said. "When you play against experienced players who understand the game, it's going to happen
"You can't get frustrated. They're clever players. A team like us who like to attack could learn from that. They do that counter-press. They lose the ball and bang, they go straight away.
"They're going to make fouls. If you do get out of it, it happens so quickly and they bring you down."