A second-half red card cost Airdrie in their 2-0 loss to Peterhead as they begin life without teen sensation Liam Coogans.The home team dominated the first half and created plenty of chances but failed to find the back of the net and paid the price.The turning point came just three minutes after the restart as Diamonds striker Keigan Parker was dismissed after receiving a second yellow card for diving.Peterhead then found another gear and took the lead in the 73rd minute when Andy Rodgers fired past Airdrie keeper Andy McNeil after some good work from Graeme Sharp.The visitors put the result beyond doubt just four minutes later as Jamie Redman found substitute David Cox and he opened his account for the season.