Manchester City head coach Manuel Pellegrini was left looking for answers after Vincent Kompany suffered yet another injury blow.
The Citizens skipper lasted just nine minutes as a second-half substitute during the 4-1 home win over Sunderland on Boxing Day with a recurrence of a long-standing calf problem.
That left Pellegrini, who had earlier been looking forward to seeing Kompany back in action for the first time since early November, frustrated and preparing to be without the central defender for another spell.
He told reporters: "The only pity was Vincent Kompany's injury. Yes, it is a calf.
"He was ready to return. I did not want him to play the whole game because we have to play so many games. He had a good warm-up, he was working during the week with normality.
"It is really difficult to understand what happened. The most important thing is to understand why this happens – that is the most important to focus on now.
"We will see with the doctor's report, but it is the same injury, the same calf."
Among the positives for Pellegrini in the resounding win over the Black Cats was another superb display by former Chelsea and Wolfsburg forward Kevin De Bruyne, who scored once and assisted in another two goals.
The Belgium international has scored ten goals in 23 appearances so far for the Citizens, while also having a hand in setting up as many goals again.
Meanwhile, City are back in action on Tuesday evening when they head to the King Power Stadium to take on Premier League leaders Leicester City, who suffered a 1-0 defeat at Liverpool on Boxing Day.
That allowed the Citizens to close to within three points of the Foxes, with Arsenal two points behind Leicester in second after being mauled 4-0 at Southampton.
City are now 5000/1 to win the Premier League title this season, with Leicester 1/10000 and the Gunners 5000/1.
Looking for more from us? Follow us on Twitter, like us on Facebook or +1 us on Google+ for fun competitions, special offers & much more!
Don't forget, all Premier League matches are covered by the us Euro Soccer Bonus, where you could earn a bonus of up to 100% on your returns on pre-match accumulator bets. T & Cs apply.
View all Soccer betting