Kevin de Bruyne has been ruled out of Manchester City's trip to Manchester United in the Premier League tomorrow night.
The Belgian attacker has endured an injury plagued season and limped out of City's weekend win over Tottenham.
De Bruyne's had three separate spells on the sidelines this term and has only played eleven matches in the Premier League.
Manager Pep Guardiola is not sure how long the latest issue with keep the 27-year-old out for.
"It's a muscular problem, we'll see in the next days if he's getting better but for tomorrow he's not available."
Guardiola says the club's medical staff need to manage de Bruyne's fitness levels better, after a season of niggling injuries.
"It was one injury then another and another, now he's had two or three muscular problems since his knee. Normally with the competition in England they have to take the physical condition playing games, now we have to pay more attention to the little details.
"We have to see if he can play one or two more games before the end of the season. He has a lovely family, his life is incredibly well organised with training and rest.
"We'll speak with him, the doctors and the physio's for him to be fit.
"Now we have to see if he can play one or two more games before the end of the season and have a good pre-season.
"He has a lovely family so his life is well-organised. We are going to speak with him, the doctors, the physios to make sure he is safe and fit."