Premiership champions Cliftonville lost ground on leaders Linfield as they fell at home to Portadown for the second time this season.
Tommy Breslin's usually lethal strike force of Joe Gormley and Liam Boyce had an off day and it was the Ports who grabbed the goal in the 57th minute.
Gary Twigg scored his 18th of the season, netting from close-range after Darren Murray had drilled the ball in.
Portadown move up to fourth, above Glentoran on goal difference.
It was Cliftonville's first defeat in 16 league fixtures.
But it was not just down to poor finishing, as Ports keeper David Miskelly had an outstanding game.
Early on he made a superb stop from Boyce and went on to deny 30-goal striker Gormley on a number of occasions.
Boyce also struck a post with a shot in the first half.
Reds winger Chris Curran had a great chance in the second half, after being played in by Boyce, but he blazed over when one-on-one with keeper Miskelly.
Cliftonville threw everyone forward towards the end and Miskelly was called into action again to save from Diarmuid O'Carroll.