Devlin, 33, closed with a one over 72 at Hombre Golf Club in Panama City (Fla) to finish seven shots outside the top 20 and ties who progressed to next month's finals at West Palm Beach with Turner three shots outside the mark in Texas.
In the end, exactly 20 players finished on four under par 280 in Florida with former US PGA champion Shaun Micheel making it with a shot to spare in tied ninth on five under. Australia's Peter Lonard withdrew after three rounds.
Turner gave himself a fighting chance of securing Nationwide Tour status and an opportunity to fight for a PGA Tour card when he fired a third round 67 to haul himself inside the top 21 and ties at TPC Craig Ranch near Dallas.
But he could only manage a one over par 72 in the final round with three bogeys and a solitary birdie on the back nine relegating him from tied 19th to tied 33rd on one under with 23 players progressing.