Northampton Town manager Ian Sampson says his side must improve defensively.The Cobblers have conceded 11 goals in five matches but are unbeaten in their last two League games, having drawn with Port Vale and Cheltenham. [LNB]Sampson told BBC Radio Northampton: "We've had problems defensively but we've tried different partnerships and we're working hard in training. [LNB]"We're not going to use injuries as an excuse. It's a squad game and everyone gets a chance." [LNB]Peter Gilbert was the latest Cobblers defender to pick up an injury, in Saturday's 1-1 draw with Port Vale but Craig Hinton is returning to fitness and Chris McCready is back in training. [LNB]Northampton find themselves 20th in League Two as they approach the midway stage of the season. [LNB]"[Darlington] is a massive game for us and everyone at the club now," Sampson added. [LNB]"We're looking to stay unbeaten over the Christmas period."