Brentford failed to make the most of scoring inside the first five minutes as they were beaten at home by Oldham Athletic.
Myles Weston gave The Bees the lead in the fourth minute but Oldham were level within ten minutes and ahead seconds after half time.
The Latics added a third from the penalty spot and although Brentford tried to fight back, the Greater Manchester side took the points.
Brentford could not have started better, taking the lead with their first sight of goal.
Charlie MacDonald fed a ball back to Craig Woodman and he picked out a delightful through ball, Weston raced clear, rounded Dean Brill and marked his 50th start for The Bees with the opening goal.
In truth, the first ten minutes were rather scrappy but once both teams settled down there was some top class football on display in the first half, with Brentford having the better of it.
The Bees will feel they could have wrapped the game up in the first half, and they certainly had the chances.
MacDonald broke free down the left, cut inside and saw a shot blocked by Jason Jarrett.
Oldham couldn't clear, Weston fired in a cross that Nicky Forster couldn't turn in, the ball fell to Kevin O'Connor and his fierce shot was palmed away by Brill but only to MacDonald, but his goal was ruled out for offside.
Oldham had threatened an equaliser when Michael Spillane made a good late tackle when Chris Taylor looked to be clear and Ben Hamer saved a swerving Dale Stephens shot.
And they were level just before the quarter hour when Kieran Lee raced clear on the right, his cut back was perfect for Dean Furman, who slotted home from the edge of the box.
Oldham, refreshingly, did not sit on what they had and it led to an entertaining first period.
Hamer had to turn over a Dale Stephens volley and Taylor shot wide from 20 yards.
Brentford were creating the better chances, Leon Legge couldn't stab in an O'Connor corner and when the ball came back in, Forster shot over.
The Bees had the ball in the net for a third time before the half hour when Weston raced onto a MacDonald pass and cut it back for Forster to score but the game was pulled back for offside against Weston.
Spillane again tackled well when Oumare Tounkara looked to be clear but Oldham were mainly shooting from long range.
Taylor, Jarrett and Stephens all blazed off target from distance while at the other end, MacDonald fired inches over from a Forster knock back.
Lewis Grabban, making his first start after a second loan move from Millwall, shot just wide and Weston had a shot blocked by Jean-Yves M'voto.
By now, the game was really stretched, chances were coming at both ends, albeit Oldham's efforts were still mainly from distance.
Lewis Alessandra, Richie Jones, Taylor and Furman all missed the target as half time approached while Forster turned a Woodman free kick wide at the other end.
Brentford would have gone in at the break feeling unlucky not to be ahead but within seconds of the re-start they were behind.
Unofficially, it was 17 seconds - Tounkara found space on the edge of the box and flicked it through to Taylor and he had little trouble in beating Hamer from 15 yards.
Tounkara shot wide as Oldham broke while at the other end, MacDonald had a flicked header saved and Legge headed an O'Connor corner wide when unmarked.
Oldham grew in confidence after the goal, moving the ball well from side to side and continuing to attack.
Stephens shot wide for The Latics and he was given an even better chance when the visitors were awarded a penalty.
Brentford could have few complaints, Legge put in a strong tackle on Taylor and appeared to get the man rather than the ball.
Stephens drilled the spot kick under Hamer to give Oldham an unassailable lead.
Substitute Gary Alexander had a shot blocked but Tounkara could have made it four when he blasted over following a nice turn.
With Alexander joining the fray, Brentford threw caution to the wind, and lots of men forward.
Woodman cut inside and blasted a right foot shot narrowly wide and Forster had a header saved.
The Bees were almost back in it soon after when a free kick from the right from Woodman was flicked by MacDonald, but it cannoned away off the crossbar.
Oldham's main tactic in the later stages seemed to be to collect yellow cards - five in all - and raise the ire of the Griffin Park crowd.
But they defended well, and in numbers, making it difficult for Brentford to create openings.
They also passed the ball well and Woodman had to make a good late interception to prevent substitute Dean Kelly adding a fourth before the same man blasted over last on.
Forster headed on O'Connor corner wide in the dying stages and Alexander shot wide from distance before MacDonald missed the target with a good shot on the turn.
But The Bees could not break through and slipped to a third home loss of the campaign.
Brentford: Hamer; Spillane (sub Wood 80 mins) Legge, Osborne, Woodman; Grabban (sub Alexander 66 mins), O'Connor, Diagouraga (sub Bean 60 mins), Weston; MacDonald, Forster
Subs (not used): Lee, McCracken, Adams, Hunt
Bookings: Legge (64 mins)
Oldham Athletic: Brill; Lee, Jarrett, M'voto, Evina; Jones, Stephens, Furman, Alessandra; Taylor (sub Christophe 84 mins); Tounkara (sub Kelly 87 mins)
Subs (not used): Gerrard, Holdsworth, Kelly, Black, Brooke, Dickov
Bookings: Alessandra (54 mins), Lee (59 mins), Taylor (61 mins), Evina (78 mins), Tounkare (83 mins)
Attendance: 5,339 (322 away fans)
By Chris Wickham