The Croatian defender was replaced at half-time of our 4-2 victory over Crystal Palace on Saturday with only a short time to recover ahead of our quarter-final first leg on Tuesday at 20:00 (UK).
With Nathan Ake and Kyle Walker recovering from setbacks in Manchester, City do not have their usual options ahead of the game at the Santiago Bernabeu.
But the City boss says he will look for a solution and will not use it as an excuse as Madrid also have key players missing.
“He travelled but he is a doubt,” Guardiola said in his press conference.
“It is what it is. Also Madrid have [Thibaut] Courtois, [Eder] Militao and [David] Alaba, a long time they have been without players.
“Kyle unfortunately in a friendly game was injured. We would love to have him but what can I say?
“Injuries are part of a long season but unfortunately in a decisive part of the season we have a number of injuries in the same area and we have to find a solution.”
REAL MADRID V CITY | MATCH PREVIEW
In last season’s first leg in the Spanish capital, Walker and Real winger Vinicius Junior had a memorable battle throughout the game on the wing.
The Brazilian scored an opener before Kevin De Bruyne superb equaliser secured a 1-1 draw ahead of our resounding victory at the Etihad.
But Guardiola said facing the record 14-times Champions League winners is always a huge test after epic encounters in our last two seasons.
“Two years ago we went out in the last minutes, last year we won,” he added.
“We have the same managers but we have new players, they have new players.
“We have a little advantage that we play second leg at home where we feel strong and incredibly confident but we have to play 90 minutes here.
“They will press high, so aggressive. They are so dangerous. If you make good progress they will drop.
“Everybody knows, not just Pep, the strength they have on the transitions. They have incredible pace.
“At the same time, you have to try to punish them, hurt them and make them feel we are here to score goals. Real Madrid can control many aspects but we have to impose who we are.”
Among the new faces in the Madrid side is Jude Bellingham who faced City when he was with Borussia Dortmund.
Guardiola was impressed with his performances for the German side and said he is a threat after the way he has quickly settled in Spain.
“He played at 17-year-old once or twice when we face Borussia Dortmund and I said, not just the skills, but the difference is what he has in his brain and mind,” he said.
“He came to this exceptional club with Carlo who knows how to find the best position.
“Carlo found it and he has had an incredible season and he clicked quick. Not just for Madrid, for the national team too he has been brilliant. He has a long, long career ahead of him.”
