Manchester City are potentially at risk of being without key defender Josko Gvardiol for the rest of the season following the injury he sustained in Sunday's 1-1 draw against Chelsea. The Croatian defender had to be helped off the pitch in the second half, in the same game as chief centre-back partner Ruben Dias was also unable to continue, while John Stones is still sidelined.Gvardiol was left unable to continue only a few minutes into the second half after what had appeared a fairly innocuous knock as he battled for the ball. He managed to walk off, without the need for a stretcher, although was helped to do so by a member of City's medical team and Chelsea captain Reece James, whose magnanimous behaviour was likely the result of empathy born out of his own injury hell in the past.Gvardiol seemed to catch his foot on the turf, with the impact now revealed to have caused plenty of damage. A medical report from City published on Monday confirmed a "tibial fracture" – in other words, the 23-year-old has broken his right leg.Liverpool's Alexander Isak recently suffered a similar injury, fracturing a fibula.City additionally confirmed that Gvardiol will have surgery on the injury in the coming days. The assessment period "remains ongoing" and there is no official timeframe for when he might return to the pitch. However, to play for Manchester City again this season would require a full recovery and rehab to be complete in less than five months. Everything will depend on the exact severity of the problem and the success of the operation.Aside from missing hugely important club games as City try to reclaim the Premier League title playing catchup on Arsenal, just as concerning for Gvardiol on a personal level is the possibility of a knock-on impact on his World Cup dreams with Croatia. The tournament begins in mid-June and Croatia, who have finished second and third in the last two editions, are to face England, Panama and Ghana in Group L.Looking for smarter football bets? Get expert previews, data-driven predictions & winning insights with GOAL Tips on Telegram. Join our growing community now!Ruben Dias came off later in the Chelsea game and, according to Daily Mail reporting, City are running tests on the severity of a muscle injury. It is unclear how long the Portugal international might be unavailable for, but with John Stones ruled out since early December and Manuel Akanji on loan in Serie A, it leaves Abdukodir Khusanov and Nathan Ake the only fit centre-backs in the first-team squad - even Ake has to have a carefully managed workload because of ongoing fitness concerns. Vitor Reis and Juma Bah are currently on loan at Girona and Nice respectively.As an emergency measure, City have already recalled 20-year-old Max Alleyne from a loan spell at Watford. He made 16 Championship appearances for the Hornets during the first half of the season, 14 of them as a starter, and has represrnted England at various age groups up to Under-21 level. He has never made a first-team appearance for City, though.Add GOAL.com as a preferred source on Google to see more of our reportingAlthough City's eye this month has been trained on completing a £65 million ($88m) deal for Bournemouth forward Antoine Semenyo, developments surrounding Gvardiol and Dias are forcing them to consider dipping into the market for a central defender too. City were already linked with Crystal Palace captain Marc Guehi, but things could now accelerate.Guehi, who almost joined Liverpool in September, is out of contract at the end of this season and so Palace face losing the England international as a free agent if they don't cash in now. It was originally thought that City would wait for information to come back on Gvardiol and Dias before making a decision on Guehi, likely to be after the former's imminent surgery. But with a swift return unlikely, City may have their hand forced or risk playing the second half of the season with virtually no defensive cover.