A Marc McNulty goal helped Coventry climb into the Sky Bet League Two automatic promotion places with a 1-0 win against struggling Chesterfield.McNulty hit the winner in the 14th minute after he curled past Jake Eastwood.It came in a half of few chances with Lee Burge's save to deny Andy Kellett's long-range strike on 25 minutes the only other shot of note.Joe Rowley smacked the post for the visitors with a cross seconds after the restart.Laurence Maguire headed Kellett's cross wide on 50 minutes, before Devon Kelly-Evans shot over for the hosts on 67 minutes.Kellett shot wide when he should have scored a minute later after an attempted clearance fell kindly.McNulty missed a great chance to wrap it up on 73 minutes when his shot was saved after a great pass by Tom Bayliss.Burge easily saved Diego De Girolamo's header four minutes later as Chesterfield's hopes faded.Their task got even harder when Scott Wiseman was sent off for a second booking after he fouled Jordan Ponticelli with 10 minutes to go.