Manchester City fear captain Vincent Kompany could be sidelined for up to six weeks with his groin injury.
The influential defender was ruled out for at least a month after limping out of City's season-opening Barclays Premier League win against Newcastle on August 19.
Kompany has said he hopes to return inside a month - possibly for the trip to Stoke on September 14, or the start of the Champions League campaign three days later - but manager Manuel Pellegrini has warned he will not be rushed. Pellegrini said: "(There is) nothing new with Vincent.
"Doctors said from the beginning it could last for six weeks. We will see next week how he improves but less than one month is impossible."
On the positive side, fellow central defender Matija Nastasic is fit to start this weekend's clash against Hull.
Having only just recovered from an ankle injury, the Serbian was an unused substitute in last Sunday's defeat at Cardiff while midfielder Javi Garcia filled in at the back.
Pellegrini, speaking at his pre-match press conference, said: "Yes, Nastasic is able to play from the beginning.
"I think that Javi didn't do bad but he normally plays in midfield.
"It is Nastasic's position so I think it is better for the team."
The injuries to Kompany and Nastasic, as well as another to Micah Richards, have led to increased speculation that City could sign another defender before next Monday's transfer deadline.
City have been heavily linked with Atletico Madrid's Martin Demichelis, who worked with Pellegrini at Malaga, and a deal could move closer if the Spanish side secure Ajax's Toby Alderweireld as a replacement.
There have also been reports linking City with Porto's £38million-rated Eliaquim Mangala, but that would seem unlikely given the apparent interest in Demichelis, as well as the cost.
Pellegrini said: "There are a lot of names linked with Manchester City. It is not my duty to answer (on) all those names.
"We will see next Monday what will happen.
"We have some days to bring someone in. We will see what we can do."
City spent almost £90million earlier in the summer acquiring Fernandinho, Jesus Navas, Alvaro Negredo and Stevan Jovetic.
With that business long done, and the likely addition of one defender, Pellegrini insists this deadline day will not be a busy one at the Etihad Stadium.
He said: "For Manchester City, no, for the rest of the teams, I don't know."
Pellegrini is anxious to get back to winning ways against Hull after unexpectedly slipping up against another of this season's promoted teams in Cardiff.
That match was painted as a rude awakening to the toughness of the Premier League to Pellegrini, but the Chilean is dismissive of such talk.
He said: "I don't need to lose a game with Cardiff to know about the Premier League.
"In football - I know perfectly - it is very difficult in some moments to defend set-pieces.
"It was a bad game that way but we must improve in the next game because, in every league, it is a very important thing.
"I saw Hull's first two games in the Premier League. I thought they played well against Chelsea, especially in the second half.
"I am sure we will have a very difficult team here, also defending well and trying to counter-attack.
"We will have to play a very good game if we want to win."
Pellegrini has changed City's usual routine to train at the Etihad Stadium on a day prior to a home match, rather than at Carrington.
He said: "I did (this) also for the other game we played at home.
"I think it is better for the team to work one day here at the stadium."
City now know their opponents for the Champions League group stages, which start next month.
Pellegrini's men were drawn against Bayern Munich, CSKA Moscow and Viktoria Plzen in Group D, a section from which they might be confident of progressing.
The draw certainly seems kinder for City than in the previous two seasons, when they have failed to reach the knockout rounds.
But Pellegrini said: "I think all are difficult groups. We have chances to go to the round of 16 if we play well, (not) because we have weaker teams.
"It is one of our targets. We will hope we can do it and continue in the Champions League this year, further than in other years."