Goalkeeper Colin Doyle frustrated play-off chasing Sheffield United as he earned Blackpool a 0-0 draw at Bloomfield Road.The hosts' shotstopper was in fine form throughout, denying Connor Sammon and Jamal Campbell-Ryce in either half to earn lowly Blackpool a share of the spoils.The Blades squandered a great chance to take the lead within the first minute when an unmarked Sammon turned Paul Coutt's cross wide from 12 yards.Brad Potts then forced a smart stop from Blades goalkeeper George Long with a powerful 20-yard drive after 12 minutes in an end-to-end opening.Sammon thought he had scored with a powerful drive from 12 yards after 27 minutes, but Doyle produced a wonderful save low to his right.The Seasiders threatened after 53 minutes when Danny Philliskirk teed up Jim McAlister six yards out, but his tame effort was easily held by Long.And the hosts almost took the lead once more after a brilliant turn and shot from 18 yards by debutant Uche Ikpeazu landed on the roof of the net after 66 minutes.Nigel Adkins' men had an opportunity to win it through Campbell-Ryce in the 75th minute, but Doyle's save meant it finished goalless.