Manchester City are sweating on the extent of a "stupid" injury that threatens to rule Sergio Aguero out of a key stage of the title run-in.
When Aguero missed last weekend's draw at Stoke, Blues assistant-boss David Platt dismissed it as a minor ankle injury the club's #38million record signing had suffered in training the day before.
Now manager Roberto Mancini has revealed the problem to be more serious, and certainly more complicated.
Mancini was cryptic in his explanation, leaving the significant fact about exactly what has happened to Aguero unanswered.
However, he did confirm the South American would miss Saturday's encounter with Sunderland at the Etihad Stadium and could not say for certain whether Aguero will have recovered by the time City head to Arsenal on April 8.
"Sergio has a problem in his foot, but it is better we don't talk about it because it is a stupid injury," said Mancini.
"It is not his fault but he can't play with this injury for a week, 10 days, two weeks? I don't know.
"For us it is a big problem because we lost Sergio against Stoke and he can't play. We hope we can recover him for Arsenal, but I don't know if it is possible.
"I'm really disappointed and I hope it won't be weeks."
Mancini declined to elaborate but even the bare details raise significant questions as he had already stated that Carlos Tevez was not fit enough to be handed a starting spot against a Sunderland side that have already beaten City once this season.
That leaves Edin Dzeko, who has scored just five times in his last 25 appearances and none in his last six, and the enigmatic Mario Balotelli as Mancini's only other forward options.
Balotelli's tendency towards the bizarre continued earlier this week when he appeared at a press conference for former club Inter Milan as they unveiled Andrea Stramaccioni as their successor to sacked Claudio Ranieri.
On Wednesday, pictures were circulated of an apparent bust-up between Mancini and Balotelli at City's Carrington training complex.
At least with the latter issue, Mancini had an explanation.
"I spoke with him during training because I was explaining some situation on the pitch," he said.
"At the press conference he was there like a journalist. It is better you ask him why but he had two days off."
Mancini confirmed that skipper Vincent Kompany had recovered from a calf problem but fellow central defender Joleon Lescott was still sidelined by a hip injury.
Martin O'Neill has insisted Sunderland cannot regard themselves as an established Barclays Premier League club simply because they secured a top-10 finish last season.
The Black Cats dragged themselves into 10th place on the final day of the campaign, largely as a result of derby rivals Newcastle's failure to hold on to a 3-0 lead over West Brom, to fulfil the mission on which they had set out in the previous August.
However, O'Neill arrived on Wearside in December to inherit a club flirting with relegation, and the recovery he has inspired since sees them heading for City sitting in eighth and targeting an improvement this time around.
O'Neill said: "I have heard we want to be a top-10 team, a top-10 football club, and that's great, it's a great ambition.
"But you have to strive for that. You just don't turn up at the start of the season and say, 'We are a top-10 side' and things fall in accordingly.
"You don't realise. You have to battle every single week for that, every week, and this is the point.
"There is no such thing as somebody being established - I will probably excuse the top six teams, who consider themselves in terms of the money stakes and all that to be very, very strong now, stronger than ever before, perhaps.
"But you have to start again and you have to go and fight from the opening day of the season right to the end.
"Only then when you have finished the season, if you are lucky enough to have done so well, then you can turn around and say, 'That was good'.
"Then you start the next year again."
Full-back Wayne Bridge is ineligible to play against his parent club, and either Kieran Richardson, who has returned to light training after a calf injury, or Jack Colback, who sat out in midweek because of the birth of his first child, are in line to deputise.
However, John O'Shea is definitely sidelined and skipper Lee Cattermole is battling against a knee injury for a game in which victory would give Sunderland an unlikely double following their 1-0 win over City on New Year's Day.