Speaking in his pre-match press conference, the Blues boss admitted a strong first-leg advantage provides the perfect chance to make changes, but explained Vincent Kompany, Ilkay Gundogan and Bacary Sagna are not yet in contention.
“In terms of long-term injuries, Vincent Kompany and Ilkay Gundogan have little problems,” he said. “We have ten days to work with them and improve their physical conditions.
“Hopefully, when we come back from the international break, they will be a full part of our training sessions.
“Bacary Sagna is not available. Against West Ham is it not possible for him to play. Maybe at Old Trafford.
“Joe Hart and Yaya Toure have a chance to play [against Steaua].
“We had 28 players in the training session. It’s difficult for me to leave players who deserve to play out. We’ve played tough games in the last week. I will make some rotations with the players.”
Despite a 5-0 advantage from the away clash, Guardiola also warned against complacency, insisting it is not acceptable to him.
He added: “I have lot of respect for the opponents and I know what can happen in football.
“Everybody knows nothing is done until it is done. We are so happy with 5-0 but we have to take the opponent seriously and try to win the game.
“Look at the Champions League final with Liverpool and AC Milan - 3-0 at half-time and that was a Milan with many experienced players.
"I said to the players: 'I am sorry but we are not already in the Champions League. We could play and receive a red card inside ten minutes… then a penalty… then another red card ten minutes later!'
“We have a huge advantage but we will not play thinking it’s done."
When asked of his thoughts on his side’s impressive start to life under his leadership and new style, he replied: “Results help us to be more calm. We have to try to play as good as possible to achieve the result.
"I was pretty sure we would be able to do that. Most of the players get it quickly, though we are a little bit surprised how quickly it has happened.
“We have to improve a lot but in the short time we have been together, we have made very good things.”
Also present at the conference was Kelechi Iheanacho, who recently penned a new deal with City.
Quizzed on his feelings having committed his future to the club, he declared: "I’m very happy to sign a new contract. I'm ready to work hard.
"You need to work hard as a player to get your chance and I’m doing everything I can to get my chance."
After Guardiola stated he may field young players in the line-up for Steaua, Kelechi asserted he would be delighted to be selected.
"If I’m in the team, I’m going to do my best and try to do everything we do in training," he continued.
"I haven’t had any private discussions with Pep. He has the final decision on the team and I have to work hard to be in his team.
"We have a target as a team but we don’t have individual targets. We’re working hard together to achieve the team’s targets."
The Nigerian was also asked to describe his incredible debut campaign, and spoke of his pride to be able to play alongside the likes of Sergio Aguero.
"It was a dream come true to play last season," he smiled. "I’ll be hoping to achieve more this season for the team.
"Sergio is a great striker and I’m learning from him. It’s not pressure for me to play alongside him.
"Everyone is working together as a team. As a striker you need to defend as well so it’s not just about scoring goals."