Chesterfield stayed on the verge of a play-off place with a comprehensive 3-0 victory over Port Vale at the Proact Stadium.Armand Gnanduillet gave them a first-half lead before a penalty from Eoin Doyle and Charlie Raglan's first goal for the club completed an impressive display from Paul Cook's team.The teams were level on points before kick-off but Chesterfield struck first when Romuald Boco crossed from the left and Gnanduillet scored with a downward header from eight yards.Vale had a chance in the 21st minute when Mark Marshall got behind Chesterfield on the right, but his cross was headed over from 10 yards by Louis Dodds.Chesterfield were playing the better football and Doyle just failed to connect with Sam Morsy's cross in the 49th minute, but deservedly increased their lead in the 61st minute when Doyle was tripped by Freddie Veseli and the striker sent Vale goalkeeper Chris Neal the wrong way with the penalty.Any chance Vale had of getting back in the game vanished in the 70th minute when Raglan dived to head in a corner for his first Chesterfield goal.