Knee injury stalls Carr Birmingham skipper Stephen Carr will definitely be unavailable when they host Bolton at St Andrew's. The veteran defender has been ruled out for up to six months after undergoing surgery on his knee. Carr had been on the verge of a first-team comeback following a thigh complaint, but is now sidelined until at least March after scans showed his knee suffered severe damage. Striker Nikola Zigic and defender Curtis Davies may both return to the starting XI having fully recovered from foot and ankle injuries respectively. Midfielder Darren Ambrose was again absent for Saturday's draw at Nottingham Forest and remains a doubt. Keith Fahey was on the bench for that fixture having returned from a troublesome groin injury and the midfielder could be recalled to Lee Clark's starting XI. Bolton manager Owen Coyle expects to select from an unchanged squad. David Ngog made his first appearance of the season in Saturday's 2-1 triumph over Watford at the Reebok Stadium following a back problem and, although the former Liverpool striker was withdrawn due to cramp with an hour gone, Coyle expects him to take part against Lee Clark's men. Summer signing Matt Mills opened the scoring on Saturday as Wanderers recovered from three games without a win in all competitions, and the former Leicester centre-back is expecting a thorough midweek examination in the second city. "Birmingham are a good side - if you look at their squad there is a lot of Premier League experience, let alone Championship," he told Bolton's official website. "It will be a tough test and we have to be ready." Elsewhere the Trotters have no new injury problems, with knee-injury victims Stuart Holden, David Wheater and Josh Vela remaining long-term absentees.