Mark Hughes, the Manchester City manager, has made no secret of his desire to strengthen his squad in January, but the need for recruits became more pressing yesterday after Martin Petrov, the winger, had knee surgery that will rule him out for up to four months.

Hughes has submitted his list of transfer targets to Sheikh Mansour, the club's owner, and Khaldoon al-Mubarak, the chairman, and will hope that he can get the five or six players he wants as he wrestles with a porous defence and mounting injury list.

Petrov joins Valeri Bojinov, the striker, who is recovering from a snapped Achilles tendon, on the long-term injury list, and with Joe Hart, the goalkeeper, out for up to four weeks with a sprained left ankle and Michael Johnson, the midfield player, well short of match fitness after a groin injury, the transfer window cannot come soon enough for Hughes.

Too many leading players are struggling for form, among them Richard Dunne and Micah Richards, the defenders, and Jô, the striker, who was included in the reserve-team squad for the game at home to Bolton Wanderers last night. With Arsenal and Manchester United up next in the Barclays Premier League, things may get worse before they can get better.

The 2-2 draw away to Hull City on Sunday represented an improvement of sorts, although again City's deficiencies in defence were laid bare. They have conceded 22 goals in 13 league matches this season, 15 of which have been shipped in their past eight league matches.

With many senior players struggling for consistency, Robinho's form since his British-record £34.2 million move from Real Madrid has at least been a source of comfort and the manager intimated yesterday that the Brazil forward could be made captain in the future. Robinho was handed the armband in the absence of the suspended Dunne against Hull City on Sunday.

“The armband was something that he deserved and relished,” Hughes said. “Who knows if he is long-term captain material? He has done his claims no harm with what he did [in the 2-2 draw] at the KC Stadium.”