Former Arsenal attacker Paul Merson has urged Manchester City to replace Fernandinho "very quickly" due to concerns over the ageing midfielder.
The Citizens' loss of form has coincided with the 33-year-old's absence from the side, having missed the defeats to Crystal Palace and Leicester City through a thigh injury.
City have no obvious like-for-like replacement for Fernandinho in the engine room, which Merson believes is a serious problem that the champions must rectify as a matter of priority.
"If he doesn't play, they haven't got anybody to replace him," he told Sky Sports News. "They've got everybody covered for a position, bar there [in defensive midfield].
It's been proven. He keeps it simple and he knows how to break the game up, and when he gets the ball he then gives it to the players who do the business.
"I think he's been a massive miss and I think City have a big problem coming up. He's 33 years old. As the years go on, he's not going to able to play every game. I think they need to replace him very quickly, and if they don't, they're going to struggle."
Ajax ace Frenkie de Jong is believed to be high on Pep Guardiola's transfer wishlist, but no deal is likely to go through until the end of the season at the earliest.