Matthew Clarke scored against his former club as Ballymena United inflicted a first defeat of the season on Linfield in a 1-0 win at the Showgrounds.
Clarke scored in the 21st minute as he headed home Ben Kennedy's superb cross.
Linfield's first league defeat of the season leaves David Healy's side in sixth place, seven points off leaders Glentoran but with a game in hand.
Ballymena, who bounced back from a late 3-2 loss at Cliftonville, are now in fourth place, two points ahead of the Blues.
Ballymena almost opened the scoring inside the opening 50 seconds when Success Edogun seized upon a misplaced pass from Dane McCullough and raced into the penalty area but he was denied by a timely tackle from Ben Hall.
Linfield also had an early opening as Kieran Offord found half a yard of space in the penalty area but his low shot was beaten out at the near post by Sean O'Neill.
The visitors also went close when Kyle McClean's cross from the left was flicked on and came to Isaac Baird at the back post but the in-rushing midfielder took a heavy touch and the chance disappeared.
The home side grabbed the lead on 21 minutes when Kennedy crossed to the back post and Clarke rose highest to head home against the club he made 411 appearances for, with keeper Chris Johns only able to push his effort into the roof of the net.
Buoyed by that goal, the Sky Blues went close again as Kennedy's cross was flicked on by Calvin McCurry into his own path but the striker's volley was straight at Johns.
Linfield again had a lot of the play in the second period but aside from an Offord shot straight at O'Neill and a miscued Chris McKee cross which the United keeper had to palm away, the visitors struggled to penetrate the Ballymena rearguard.
The home side might have doubled their lead in the final minute when substitute Ryan McNickle's shot came back off the inside of the post but Ballymena held on to end a run of three straight league defeats and move back into the top half of the table.
Image source, Press Eye
