On top of that, the boss spoke of his concern about the energy levels of several others after an action-packed start to the 2023/24 season.
He looks set to tread carefully when he picks his team to face the Magpies although he admitted that returning winger, Jack Grealish, will feature.
After the Nottingham Forest win, he said: “Now I’ll go home, tomorrow training and day off afterwards, and prepare the game in Newcastle.
“We’ll see how many players we’ll have available. It will be good for Jack [Grealish] to take minutes, and of course some players have a lot of minutes, they are not going to play against Newcastle. That’s for sure.
“Carabao Cup is perfect when you are in the beginning of the season because the games at the beginning of the season you have all the squad, deep squad, for the guys that don’t play regularly, they have to play the minutes. That’s perfect.
“But we have a lot of injuries, I’m not going to waste one percent of energy for Carabao Cup, like Kyle Walker for example, like Ruben [Dias], who have played 90 minutes for the national team, 90 minutes, because they are exhausted already. And we cannot lose it.
“That’s why we’re going to play with the guys who need it, maybe from the Academy, maybe if my back is getting better, [I can play] maybe a few minutes. We’ll see.”
In positive news, Guardiola says he expects to see Kovacic back soon.
The Croatian international missed the last three games, victories over West Ham, Red Star Belgrade and Nottingham Forest.
But the manager, speaking straight after the Forest win, is hopeful of seeing Kovacic return shortly.
“Soon. Soon. Tomorrow [Sunday], I think he’s going to train with the team already,” said the boss.
“Today [Saturday] he made a partial [training], but we didn’t take the risk with the injury he had in the front of the leg – it’s riskier than other places.
“But tomorrow [Sunday] he’ll start to train.”