Fabian Delph could miss the start of the season after picking up a hamstring injury in yesterday's 4-1 defeat by Real Madrid.
And with Fernandinho only returning to training next week, after his involvement in the Copa America, that will leave the central midfield down to the bare bones of Yaya Toure and Fernando.
Delph was stretchered off after going down under a revenge challenge from Madrid star Luka Modric - and could be seen mouthing to team-mates that it was his hamstring.
But the Blues will assess it properly after they have flown to Vietnam for the next leg of the tour tomorrow.
"Unfortunately Fabian had a problem with his hamstring in the first few minutes of the game," said manager Manuel Pellegrini.
"It would have been useful for him to play 45 minutes but this injury is not the best news, as he was just starting the season with our team."
The game was goalless when Delph went off after 18 minutes. Karim Benzema's volleyed opener was followed by goals from cristiano Ronaldo and Pepe, before Yaya Toure pulled a goal back. Denis Cheryshev made it 4-1 with a tap-in.