Manchester City will be without influential midfielder Kevin De Bruyne for Wednesday's EFL Cup clash against rivals Manchester United at Old Trafford.
Belgium international De Bruyne was substituted at half-time during Saturday's 1-1 draw at home to Southampton after taking a knock to the calf.
The 25-year-old opened the scoring when City claimed a 2-1 win over United last month but Guardiola told a pre-match news conference he had "no way" of playing in the latest derby showdown.
"He had a knock on the leg and he cannot play," Guardiola said, before casting doubt on De Bruyne's participation in City's matches over the coming week.
"Hopefully [he can face] West Brom and Barcelona [but] he's a doubt even next weekend.
Right-back Pablo Zabaleta remains a major doubt after suffering a gashed foot in the 4-0 Champions League loss at Barcelona last week, while club captain Vincent Kompany will be treated with caution after coming through his latest injury comeback unscathed versus Southampton.
"Pablo, I think not," Guardiola explained. "Vincent, I think he can but I don't know if he will."
Guardiola pledged to rotate his line-up – seemingly opening the door to youngsters such as Aleix Garcia, who scored his first senior goal against Swansea City in the previous round.
But the former Barcelona boss is well aware of the high-stakes on the line in a derby battle as his Premier League leaders aim to turn around a run of five matches without a win in all competitions.
"A derby is a derby," he said. "It's always special and so we are going to play a game like a game.
"It's a special game. We're going to play seriously like we always do since my period here and try to win the game.
"We're going to rotate, yeah - several [reserve] players are going to play for sure. First because they deserve, second because the last game was a tough, tough game.
"Against Southampton the people [players] were tired. I will still decide which guys because I need today to see the players in a training session."
United suffered a chastening 4-0 defeat to Chelsea on Sunday but Guardiola rejected the notion that this represents a fortuitous time to face his old Clasico adversary Jose Mourinho.
"Always expect the best from United," he added. "With the quality and experience of Jose and it's United - Man United! That means a lot from my experience as a football player and coach.
"It doesn't matter how you play. It's always difficult. That's nice.
"It will be difficult when they come here to the Etihad [in the league] so it's a physical team, very good on the counter-attack with [Marcus] Rashford and [Anthony] Martial.
"I don't have doubts about the quality of United. We've seen how difficult it is to win every single game."
