De Bruyne, who was rested in the midweek Carabao Cup quarter-final success at Arsenal, captained the side to victory, while Aguero continued his comeback from injury with a cameo display from the bench.
Guardiola was delighted with the contribution of both players but - previewing Monday's trip to Everton, which takes place 48 hours after the Newcastle win - highlighted the importance of rest and recovery.
“We will test again - all of us - and hopefully, the day of the game against Everton, we can be ready.
“We thought about starting with Sergio (against Newcastle). We need him, I need him.
“(On Saturday) I had very good news in general: the fact he played for 15, 20 minutes and we saw him sharp, dynamic and good.
“It’s incredible news for us – we need him. Absolutely. We’re looking forward to him coming back but at the same time, we have to be careful.
“We cannot do what we did in the past when he came back and was injured. I want to handle the minutes.
“(Against Newcastle) I saw him do well, especially in his mind. I love this guy! He’s an incredible person and we need him.
“In saying that, Ferran Torres made an incredible job. We cannot forget he is a winger, playing in a position that is not usual.
“He's a winger making different actions. It’s not normal playing this position but he’s helping a lot with his movements and runs in behind.”
“He is an outstanding player and I know how important he is for us. Sometimes, like in the game against Arsenal, he didn't travel.
“I prefer to have him fit for the Premier League, especially now the Champions League is over, and focus on the Premier League.
“Other competitions are important but we don't want to be so far from the top of the Premier League.
“We have one game (in hand) against the 'surprise of the competition - Aston Villa are doing incredible.
“It will be an incredibly tough game against them but in the way we are going to play, we are going to find our rhythm and be close to the top of the league.
“Hopefully, we will arrive in the last eight or 10 games being there to fight against the teams above us.”