Injury-hit Birmingham held at home by struggling BoltonInjury-hit Birmingham were held to a goalless draw by Bolton in the Sky Bet Championship clash at St Andrew's. The Blues again suffered after losing the services of skipper Michael Morrison and Cheikh N'Doye as a result of first-half injuries.But Bolton, still without a win in their first season back in the second tier, could take a lot of encouragement from taking a valuable point. A reconstructed Bolton built on their early play when they mounted several promising attacks against a Birmingham side which again made a slow start.They were nearly caught napping by a Adam Armstrong header, while skipper Darren Pratley had a low shot blocked by Morrison.David Cotterill made Birmingham's first attempt to break the deadlock but Andrew Taylor produced a desperate dive to block the shot.Birmingham's best chance of opening their account occurred following a long clearance by goalkeeper David Stockdale. Clayton Donaldson anticipated the high bouncing ball which deceived the Bolton defence but his angled shot whistled over the bar.Birmingham discovered more flair with Cotterill seeing one effort deflected just wide of the post by Bolton defender Reece Burke.Birmingham lost their skipper Morrison with a bleeding nose which resulted him departing to the dressing room for treatment and being replaced by Ryan Shotton, who is reportedly being lined up for a move to Middlesbrough.Bolton's limitations became evident as they were repeatedly pushed back onto the defensive by Birmingham's increasing pressure generally inspired by the industrious Craig Gardner.Armstrong was a tireless worker for Bolton and went close with a smart header from a Filipe Morais cross as the game cried out for a spark to lift the game out of the doldrums.Birmingham, who drafted in Lukas Jutkiewicz for the injured N'Doye, went through a poor spell when they completely lost their shape to enable Bolton to make some positive attacking progress.Newcomer Isaac Vassell, a recent signing from Luton, made a quiet first appearance as a substitute for Donaldson in the 72nd minute. The striker used his pace to good effect but ran up against a solid Bolton defence.